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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Reversible Oxidation Quantified by Optical Properties in Epitaxial Fe2CrO4+d Films on (001) MgAl2O4

We report on the structural and optical properties of Fe2CrO4+d epitaxial films grown by molecular beam epitaxy on MgAl2O4 (001) as a function of ?. The average Fe valence can be correlated with the out-of-plane lattice parameter and the extent of light absorption in the infrared spectral region. Over-oxidized films (0 < d < 0.5) exhibit reduced lattice parameters and suppressed infrared absorption. We discuss the behavior of a novel infrared transition at ~0.6 eV in stoichiometric Fe2CrO4 films deposited on MgAl2O4 (MAO) at or above 400 °C. This research provides new insight into the atomic structure, optical processes, oxidation states, electronic structure, and application potentials of Fe2CrO4+d.

ellipsometry, Epitaxy, thin film, oxidation, reduc↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–61°. There is three shorter (1.92 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There is three shorter (1.93 Å) and one longer (1.97 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.00 Å) and three longer (2.10 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.93 Å) and three longer (1.96 Å) Mg–O bond length. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.03 Å) and three longer (2.08 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is one shorter (1.95 Å) and three longer (1.96 Å) Mg–O bond length. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There is three shorter (1.97 Å) and one longer (2.00 Å) Mg–O bond length. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.96 Å) and one longer (2.01 Å) Mg–O bond length. There are eight inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.04 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.07 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.95 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is three shorter (1.84 Å) and one longer (1.85 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.91 Å) and three longer (1.95 Å) Al–O bond length. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.98 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.94 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is three shorter (1.83 Å) and one longer (1.86 Å) Al–O bond length. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fifth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are six inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There is three shorter (1.93 Å) and one longer (2.00 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.01 Å) and three longer (2.10 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There is three shorter (1.93 Å) and one longer (1.97 Å) Mg–O bond length. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.03 Å) and three longer (2.08 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. There is one shorter (1.93 Å) and three longer (1.96 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–61°. There are three shorter (1.97 Å) and one longer (2.05 Å) Mg–O bond lengths. There are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.04 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.07 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.91 Å) and three longer (1.94 Å) Al–O bond length. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.99 Å. In the fifth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is three shorter (1.84 Å) and one longer (1.86 Å) Al–O bond length. In the sixth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is three shorter (1.82 Å) and one longer (1.87 Å) Al–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the tenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the twelfth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are six inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–62°. There is three shorter (1.93 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedral tilt angles are 59°. There is one shorter (1.96 Å) and three longer (1.97 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.11 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.96 Å) and one longer (2.01 Å) Mg–O bond length. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.93 Å) and three longer (1.96 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.97 Å) and one longer (2.00 Å) Mg–O bond length. There are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. All Al–O bond lengths are 1.83 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.98 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.93–1.95 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.94 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.06 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.95 Å) Al–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the second O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra. In the third O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the fourth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the fifth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the sixth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 tetrahedra. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the tenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the twelfth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six equivalent AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.07 Å) Mg–O bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There is three shorter (1.83 Å) and one longer (1.91 Å) Al–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Mg2+ is bonded to four equivalent O2- atoms to form MgO4 tetrahedra that share corners with twelve equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Mg–O bond lengths are 1.96 Å. Al3+ is bonded to six equivalent O2- atoms to form AlO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six equivalent AlO6 octahedra. All Al–O bond lengths are 1.94 Å. O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are four shorter (2.03 Å) and two longer (2.06 Å) Mg–O bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with six equivalent MgO6 octahedra and corners with six equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–57°. There is two shorter (1.79 Å) and two longer (1.85 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent AlO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with four equivalent MgO6 octahedra. There is two shorter (1.90 Å) and four longer (1.97 Å) Al–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two Al3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are twelve inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–61°. There is three shorter (1.93 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.01 Å) and three longer (2.10 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–62°. There is three shorter (1.93 Å) and one longer (1.97 Å) Mg–O bond length. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.03 Å) and three longer (2.08 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.94 Å) and three longer (1.95 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–61°. There is three shorter (1.98 Å) and one longer (1.99 Å) Mg–O bond length. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is one shorter (1.95 Å) and three longer (1.96 Å) Mg–O bond length. In the ninth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is three shorter (1.96 Å) and one longer (1.97 Å) Mg–O bond length. In the tenth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Mg–O bond lengths are 1.96 Å. In the eleventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is three shorter (1.96 Å) and one longer (1.98 Å) Mg–O bond length. In the twelfth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.96 Å) and one longer (2.01 Å) Mg–O bond length. There are twelve inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.04 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.07 Å. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is three shorter (1.84 Å) and one longer (1.85 Å) Al–O bond length. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.93 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is two shorter (1.93 Å) and four longer (1.94 Å) Al–O bond length. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.93 Å) and three longer (1.94 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.93–1.95 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.95 Å) Al–O bond length. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.99 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.94 Å) Al–O bond length. In the twelfth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is three shorter (1.83 Å) and one longer (1.86 Å) Al–O bond length. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 tetrahedra. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the tenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 tetrahedra. In the nineteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the twentieth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the twenty-first O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 tetrahedra. In the twenty-second O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–62°. There is three shorter (1.93 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.11 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.94 Å) and three longer (1.95 Å) Mg–O bond length. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is one shorter (1.95 Å) and three longer (1.97 Å) Mg–O bond length. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–61°. There is three shorter (1.98 Å) and one longer (1.99 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Mg–O bond lengths are 1.96 Å. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is three shorter (1.96 Å) and one longer (1.97 Å) Mg–O bond length. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.96 Å) and one longer (2.01 Å) Mg–O bond length. There are eight inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.07 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.93 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is two shorter (1.93 Å) and four longer (1.94 Å) Al–O bond length. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.93 Å) and three longer (1.95 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.93–1.95 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.94 Å) Al–O bond length. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.98 Å. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is one shorter (1.82 Å) and three longer (1.83 Å) Al–O bond length. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the third O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the fourth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the tenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are seven inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.97–2.12 Å. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Mg–O bond distances ranging from 1.94–2.00 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.95 Å) and three longer (1.96 Å) Mg–O bond length. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–61°. There is three shorter (1.97 Å) and one longer (1.98 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. There are twelve inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent MgO6 octahedra and corners with eight AlO6 octahedra. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Al–O bond distances ranging from 1.79–1.83 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.97 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four equivalent AlO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with four equivalent MgO6 octahedra. There is two shorter (1.81 Å) and four longer (2.04 Å) Al–O bond length. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–2.00 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–2.00 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is one shorter (1.93 Å) and five longer (1.94 Å) Al–O bond length. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.93 Å) and three longer (1.94 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is two shorter (1.93 Å) and four longer (1.94 Å) Al–O bond length. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two Al3+ atoms. In the second O2- site, O2- is bonded to three Mg2+ and one Al3+ atom to form distorted corner-sharing OMg3Al tetrahedra. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fifth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with two OMgAl3 tetrahedra, corners with six OMgAl3 trigonal pyramids, edges with two OMgAl3 tetrahedra, and an edgeedge with one OAl4 trigonal pyramid. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids. In the tenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with two equivalent OMgAl3 tetrahedra, corners with six OMgAl3 trigonal pyramids, edges with two equivalent OMgAl3 tetrahedra, and an edgeedge with one OAl4 trigonal pyramid. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the nineteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twentieth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (2.00 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–63°. There is three shorter (1.94 Å) and one longer (1.98 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.08 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.09 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with eleven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–65°. There are a spread of Mg–O bond distances ranging from 1.97–1.99 Å. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with eleven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.97–1.99 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.09 Å) Mg–O bond lengths. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There are a spread of Mg–O bond distances ranging from 1.94–2.00 Å. There are twelve inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.03 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.03 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.06 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the fifth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.80–1.85 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.05 Å. In the seventh Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–59°. There are a spread of Al–O bond distances ranging from 1.83–1.86 Å. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.90–2.02 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.99 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.99 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There is two shorter (1.89 Å) and four longer (1.95 Å) Al–O bond length. In the twelfth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is three shorter (1.82 Å) and one longer (1.88 Å) Al–O bond length. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fourth O2- site, O2- is bonded to two Mg2+ and two Al3+ atoms to form distorted OMg2Al2 trigonal pyramids that share corners with four OMgAl3 tetrahedra, corners with two OMg2Al2 trigonal pyramids, and edges with two OMg2Al2 trigonal pyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the ninth O2- site, O2- is bonded to two Mg2+ and two equivalent Al3+ atoms to form distorted OMg2Al2 trigonal pyramids that share corners with four OMgAl3 tetrahedra, corners with two equivalent OMg2Al2 trigonal pyramids, and edges with two equivalent OMg2Al2 trigonal pyramids. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with two equivalent OMgAl3 tetrahedra, corners with four OMg2Al2 trigonal pyramids, and edges with two equivalent OMgAl3 tetrahedra. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with two OMgAl3 tetrahedra, corners with four OMg2Al2 trigonal pyramids, and edges with two OMgAl3 tetrahedra. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the fourteenth O2- site, O2- is bonded to two Mg2+ and two equivalent Al3+ atoms to form distorted corner-sharing OMg2Al2 tetrahedra. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 trigonal pyramids that share corners with three OMg2Al2 tetrahedra, corners with three OMgAl3 trigonal pyramids, and edges with three OMgAl3 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 trigonal pyramids that share corners with three OMg2Al2 tetrahedra and corners with three OMgAl3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the nineteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Al3+ atoms. In the twenty-first O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 trigonal pyramids that share corners with three OMg2Al2 tetrahedra, corners with three OMgAl3 trigonal pyramids, and edges with three OMgAl3 trigonal pyramids. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are fourteen inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 52–65°. There are a spread of Mg–O bond distances ranging from 1.92–2.01 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.09 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.92–2.00 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.08 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.91–1.98 Å. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with eleven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–66°. There are a spread of Mg–O bond distances ranging from 1.97–2.00 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.08 Å. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the ninth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.98 Å) Mg–O bond length. In the tenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.09 Å. In the eleventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the twelfth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the thirteenth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are a spread of Mg–O bond distances ranging from 1.94–2.01 Å. In the fourteenth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–63°. There is three shorter (1.95 Å) and one longer (2.04 Å) Mg–O bond length. There are twenty-one inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Al–O bond distances ranging from 1.82–1.89 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two AlO4 tetrahedra, corners with four MgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.03 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.01 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Al–O bond distances ranging from 1.83–1.89 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.06 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.01 Å. In the seventh Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Al–O bond distances ranging from 1.82–1.88 Å. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.07 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.08 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.98 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.97 Å. In the thirteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.97 Å. In the fourteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–1.98 Å. In the fifteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.97 Å. In the sixteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.99 Å. In the seventeenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.96 Å. In the eighteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.90 Å) and three longer (1.97 Å) Al–O bond length. In the nineteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–2.01 Å. In the twentieth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.08 Å. In the twenty-first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with eleven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are a spread of Al–O bond distances ranging from 1.75–1.88 Å. There are forty-two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the third O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fourth O2- site, O2- is bonded to four Al3+ atoms to form distorted OAl4 trigonal pyramids that share corners with nine OMgAl3 trigonal pyramids, an edgeedge with one OMgAl3 tetrahedra, and edges with two equivalent OAl4 trigonal pyramids. In the fifth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form OMgAl3 tetrahedra that share corners with twelve OMgAl3 trigonal pyramids and edges with three OAl4 trigonal pyramids. In the sixth O2- site, O2- is bonded to four Al3+ atoms to form distorted OAl4 trigonal pyramids that share corners with nine OMgAl3 trigonal pyramids, an edgeedge with one OMgAl3 tetrahedra, and edges with two OAl4 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 trigonal pyramids that share corners with three equivalent OMgAl3 tetrahedra, corners with seven OAl4 trigonal pyramids, and edges with three OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Al3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In t

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are fourteen inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.97–2.10 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.95–2.13 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with four MgO6 octahedra and corners with eight AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Mg–O bond distances ranging from 1.94–1.97 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.92–1.97 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.06 Å. In the ninth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.91–1.97 Å. In the tenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the eleventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the twelfth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the thirteenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the fourteenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.06 Å. There are twenty-eight inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with five MgO6 octahedra and corners with seven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 50–60°. There are a spread of Al–O bond distances ranging from 1.78–1.83 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra, edges with three MgO6 octahedra, and edges with three AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.03 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AlO4 tetrahedra, edges with two AlO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.80–2.05 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with three MgO6 octahedra, and edges with three AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with five MgO6 octahedra and corners with seven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.80–1.87 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the thirteenth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Al–O bond distances ranging from 1.83–1.90 Å. In the fourteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the fifteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the sixteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the seventeenth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Al–O bond distances ranging from 1.83–1.91 Å. In the eighteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the nineteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the twentieth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the twenty-first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Al–O bond distances ranging from 1.83–1.90 Å. In the twenty-second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the twenty-third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.00 Å. In the twenty-fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Al–O bond distances ranging from 1.83–1.90 Å. In the twenty-fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the twenty-sixth Al3+ site, Al3+ is bonded to six O2- atoms to

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are ten inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–61°. There is three shorter (1.93 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–62°. There is three shorter (1.93 Å) and one longer (1.98 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.00 Å) and three longer (2.10 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.93 Å) and three longer (1.96 Å) Mg–O bond length. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.09 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is one shorter (1.95 Å) and three longer (1.97 Å) Mg–O bond length. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Mg–O bond lengths are 1.96 Å. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There is three shorter (1.97 Å) and one longer (2.00 Å) Mg–O bond length. In the ninth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is three shorter (1.96 Å) and one longer (1.98 Å) Mg–O bond length. In the tenth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.96 Å) and one longer (2.01 Å) Mg–O bond length. There are ten inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.04 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.07 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.95 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is one shorter (1.84 Å) and three longer (1.85 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.95 Å) Al–O bond length. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.93–1.95 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.95 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.99 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.94 Å) Al–O bond length. In the tenth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is three shorter (1.83 Å) and one longer (1.86 Å) Al–O bond length. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 tetrahedra. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the tenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 tetrahedra. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the twentieth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There is three shorter (1.93 Å) and one longer (2.00 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–62°. There is three shorter (1.93 Å) and one longer (1.97 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.07 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. There is one shorter (1.93 Å) and three longer (1.96 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.03 Å) and three longer (2.08 Å) Mg–O bond lengths. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–61°. There are three shorter (1.97 Å) and one longer (2.06 Å) Mg–O bond lengths. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.01 Å) and three longer (2.10 Å) Mg–O bond lengths. There are eight inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.03 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.06 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There is three shorter (1.84 Å) and one longer (1.90 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.99 Å. In the sixth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–59°. There is three shorter (1.84 Å) and one longer (1.86 Å) Al–O bond length. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.90 Å) and three longer (1.94 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is three shorter (1.82 Å) and one longer (1.87 Å) Al–O bond length. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to four Al3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the tenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the thirteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.04–2.58 Å. Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 0–51°. There are a spread of Al–O bond distances ranging from 1.85–2.00 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Al3+ atoms to form distorted OMg2Al3 trigonal bipyramids that share corners with five equivalent OMg2Al2 tetrahedra, corners with two equivalent OMg2Al3 trigonal bipyramids, an edgeedge with one OMg2Al2 tetrahedra, and edges with five equivalent OMg2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Al3+ atoms to form distorted OMg2Al2 tetrahedra that share corners with two equivalent OMg2Al2 tetrahedra, corners with ten equivalent OMg2Al3 trigonal bipyramids, and edges with two equivalent OMg2Al3 trigonal bipyramids. In the third O2- site, O2- is bonded in a distorted square co-planar geometry to two equivalent Mg2+ and four equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.17–2.56 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–59°. There are a spread of Al–O bond distances ranging from 1.87–1.96 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–59°. There are a spread of Al–O bond distances ranging from 1.86–1.97 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Mg2+ and three Al3+ atoms. In the third O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Al3 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Mg–O bond lengths are 2.11 Å. In the second Mg2+ site, Mg2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Mg–O bond lengths are 2.11 Å. In the third Mg2+ site, Mg2+ is bonded in a distorted trigonal planar geometry to nine O2- atoms. There are three shorter (2.27 Å) and six longer (2.67 Å) Mg–O bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Al–O bond distances ranging from 1.90–1.98 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Al–O bond distances ranging from 1.89–1.98 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and three Al3+ atoms to form distorted OMg2Al3 trigonal bipyramids that share corners with three equivalent OMgAl3 tetrahedra, corners with four equivalent OMg2Al3 trigonal bipyramids, an edgeedge with one OMgAl3 tetrahedra, and edges with six OMg2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded to two equivalent Mg2+ and three Al3+ atoms to form distorted OMg2Al3 trigonal bipyramids that share corners with four equivalent OMgAl3 tetrahedra, corners with four equivalent OMg2Al3 trigonal bipyramids, and edges with six OMg2Al3 trigonal bipyramids. In the third O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with four equivalent OMgAl3 tetrahedra, corners with seven OMg2Al3 trigonal bipyramids, and an edgeedge with one OMg2Al3 trigonal bipyramid. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗