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DOE OSTI2020

Materials Data on Mg3Cr6(FeO6)4 by Materials Project

Mg3Cr6(FeO6)4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two 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 FeO6 octahedra, corners with six CrO4 tetrahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 57°. There are a spread of Mg–O bond distances ranging from 2.03–2.50 Å. In the second Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share a cornercorner with one MgO6 octahedra, corners with five CrO4 tetrahedra, and edges with two FeO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of Mg–O bond distances ranging from 2.03–2.08 Å. There are three inequivalent Cr5+ sites. In the first Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with four FeO6 octahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 24–62°. There are a spread of Cr–O bond distances ranging from 1.66–1.75 Å. In the second Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with five FeO6 octahedra, and a cornercorner with one MgO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 28–56°. There are a spread of Cr–O bond distances ranging from 1.65–1.78 Å. In the third Cr5+ site, Cr5+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with three FeO6 octahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 24–65°. There are a spread of Cr–O bond distances ranging from 1.69–1.76 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one MgO6 octahedra, corners with six CrO4 tetrahedra, an edgeedge with one FeO6 octahedra, and an edgeedge with one MgO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 57°. There are a spread of Fe–O bond distances ranging from 1.93–2.11 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six CrO4 tetrahedra, an edgeedge with one FeO6 octahedra, and an edgeedge with one MgO5 trigonal bipyramid. There are a spread of Fe–O bond distances ranging from 1.95–2.13 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cr5+, and one Fe3+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr5+ and one Fe3+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Mg2+ and one Cr5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one Cr5+ atom. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to one Mg2+, one Cr5+, and one Fe3+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr5+ and two equivalent Fe3+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cr5+, and one Fe3+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cr5+, and one Fe3+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cr5+, and one Fe3+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr5+ and two equivalent Fe3+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr5+ and one Fe3+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr5+ and one Fe3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Cr8FeO16 by Materials Project

Mg3Cr8FeO16 is Spinel-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. There are one shorter (2.00 Å) and three longer (2.01 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. All Mg–O bond lengths are 2.00 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. There are one shorter (2.00 Å) and three longer (2.01 Å) Mg–O bond lengths. There are four inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent FeO4 tetrahedra, and edges with six CrO6 octahedra. There are three shorter (2.02 Å) and three longer (2.04 Å) Cr–O bond lengths. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six MgO4 tetrahedra and edges with six CrO6 octahedra. There are three shorter (2.03 Å) and three longer (2.04 Å) Cr–O bond lengths. In the third Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent FeO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six CrO6 octahedra. There are five shorter (2.03 Å) and one longer (2.04 Å) Cr–O bond lengths. In the fourth Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share a cornercorner with one FeO4 tetrahedra, corners with five MgO4 tetrahedra, and edges with six CrO6 octahedra. There are two shorter (2.03 Å) and four longer (2.04 Å) Cr–O bond lengths. Fe2+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are one shorter (1.98 Å) and three longer (2.03 Å) Fe–O bond lengths. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three equivalent Cr3+ atoms to form distorted OMgCr3 trigonal pyramids that share corners with twelve OMgCr3 trigonal pyramids and edges with three equivalent OCr3Fe trigonal pyramids. In the second O2- site, O2- is bonded to three equivalent Cr3+ and one Fe2+ atom to form a mixture of distorted edge and corner-sharing OCr3Fe trigonal pyramids. In the third O2- site, O2- is bonded to three Cr3+ and one Fe2+ atom to form distorted OCr3Fe trigonal pyramids that share corners with twelve OCr3Fe trigonal pyramids and edges with three OMgCr3 trigonal pyramids. In the fourth O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form distorted OMgCr3 trigonal pyramids that share corners with twelve OMgCr3 trigonal pyramids and edges with three OCr3Fe trigonal pyramids. In the fifth O2- site, O2- is bonded to one Mg2+ and three equivalent Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMgCr3 trigonal pyramids. In the sixth O2- site, O2- is bonded to one Mg2+ and three equivalent Cr3+ atoms to form distorted OMgCr3 trigonal pyramids that share corners with twelve OCr3Fe trigonal pyramids and edges with three equivalent OMgCr3 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMgCr3 trigonal pyramids. In the eighth O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form distorted OMgCr3 trigonal pyramids that share corners with twelve OCr3Fe trigonal pyramids and edges with three OMgCr3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgCr8Fe3O16 by Materials Project

MgCr8Fe3O16 is Spinel-derived structured and crystallizes in the tetragonal P-4m2 space group. The structure is three-dimensional. Mg2+ is bonded to four equivalent O2- atoms to form MgO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. All Mg–O bond lengths are 2.02 Å. There are two inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four FeO4 tetrahedra, and edges with six CrO6 octahedra. There are two shorter (2.03 Å) and four longer (2.04 Å) Cr–O bond lengths. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five FeO4 tetrahedra, and edges with six CrO6 octahedra. There are five shorter (2.03 Å) and one longer (2.04 Å) Cr–O bond lengths. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to four equivalent O2- atoms to form FeO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Fe–O bond lengths are 2.04 Å. In the second Fe2+ site, Fe2+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with twelve CrO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Fe–O bond lengths are 2.04 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to three Cr3+ and one Fe2+ atom to form a mixture of distorted corner and edge-sharing OCr3Fe trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form a mixture of distorted corner and edge-sharing OMgCr3 trigonal pyramids. In the third O2- site, O2- is bonded to three equivalent Cr3+ and one Fe2+ atom to form a mixture of distorted corner and edge-sharing OCr3Fe trigonal pyramids. In the fourth O2- site, O2- is bonded to three equivalent Cr3+ and one Fe2+ atom to form a mixture of distorted corner and edge-sharing OCr3Fe trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg30CrFeO32 by Materials Project

Mg30CrFeO32 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight 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 FeO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.11–2.14 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.05–2.15 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.12 Å) and four longer (2.13 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.12 Å) and two longer (2.13 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CrO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.12–2.15 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are two shorter (2.13 Å) and four longer (2.14 Å) Mg–O bond lengths. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Mg–O bond distances ranging from 2.12–2.14 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CrO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are four shorter (2.13 Å) and two longer (2.14 Å) Mg–O bond lengths. Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.08 Å) and four longer (2.22 Å) Cr–O bond lengths. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.16 Å) and two longer (2.18 Å) Fe–O bond lengths. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form a mixture of edge and corner-sharing OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the second O2- site, O2- is bonded to five Mg2+ and one Cr2+ atom to form OMg5Cr octahedra that share corners with six OMg5Fe octahedra and edges with twelve OMg5Cr octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the third O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the fifth O2- site, O2- is bonded to five Mg2+ and one Cr2+ atom to form OMg5Cr octahedra that share corners with six OMg5Fe octahedra and edges with twelve OMg5Cr octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are two shorter (2.12 Å) and two longer (2.14 Å) O–Mg bond lengths. In the sixth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the seventh O2- site, O2- is bonded to four equivalent Mg2+, one Cr2+, and one Fe2+ atom to form OMg4CrFe octahedra that share corners with six OMg4CrFe octahedra and edges with twelve OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the eighth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg4CrFe octahedra and edges with twelve OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the ninth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the tenth O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form a mixture of edge and corner-sharing OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are two shorter (2.13 Å) and two longer (2.14 Å) O–Mg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgCr4FeO8 by Materials Project

MgCr4FeO8 is Spinel-derived structured and crystallizes in the cubic F-43m 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 CrO6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Mg–O bond lengths are 2.01 Å. Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent FeO4 tetrahedra, and edges with six equivalent CrO6 octahedra. There are three shorter (2.03 Å) and three longer (2.04 Å) Cr–O bond lengths. Fe2+ is bonded to four equivalent O2- atoms to form FeO4 tetrahedra that share corners with twelve equivalent CrO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Fe–O bond lengths are 2.02 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three equivalent Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMgCr3 trigonal pyramids. In the second O2- site, O2- is bonded to three equivalent Cr3+ and one Fe2+ atom to form distorted OCr3Fe trigonal pyramids that share corners with twelve OMgCr3 trigonal pyramids and edges with three equivalent OCr3Fe trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgCrFeO4 by Materials Project

MgFeCrO4 is Spinel-derived structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with six equivalent CrO6 octahedra and corners with six equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. There are two shorter (2.00 Å) and two longer (2.01 Å) Mg–O bond lengths. Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six equivalent MgO4 tetrahedra, edges with two equivalent CrO6 octahedra, and edges with four equivalent FeO6 octahedra. All Cr–O bond lengths are 2.04 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six equivalent MgO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with four equivalent CrO6 octahedra. All Fe–O bond lengths are 2.05 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+, two equivalent Cr3+, and one Fe3+ atom to form a mixture of distorted corner and edge-sharing OMgCr2Fe trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+, one Cr3+, and two equivalent Fe3+ atoms to form a mixture of distorted corner and edge-sharing OMgCrFe2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg30CrFeO32 by Materials Project

Mg30CrFeO32 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight 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 MgO6 octahedra, corners with two equivalent CrO6 octahedra, corners with two equivalent FeO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.07–2.14 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.12 Å) and four longer (2.14 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.10 Å) and four longer (2.15 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Mg–O bond lengths are 2.14 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CrO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.12–2.15 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.13–2.15 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mg–O bond distances ranging from 2.12–2.15 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CrO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Mg–O bond distances ranging from 2.12–2.16 Å. Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.11 Å) and four longer (2.22 Å) Cr–O bond lengths. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.13 Å) and four longer (2.18 Å) Fe–O bond lengths. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form OMg5Fe octahedra that share corners with six OMg5Fe octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the second O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg5Fe octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the third O2- site, O2- is bonded to five Mg2+ and one Cr2+ atom to form a mixture of corner and edge-sharing OMg5Cr octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the fifth O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form a mixture of corner and edge-sharing OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the sixth O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form a mixture of corner and edge-sharing OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are two shorter (2.12 Å) and two longer (2.14 Å) O–Mg bond lengths. In the seventh O2- site, O2- is bonded to five Mg2+ and one Cr2+ atom to form OMg5Cr octahedra that share corners with six OMg5Fe octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. The O–Mg bond length is 2.07 Å. In the eighth O2- site, O2- is bonded to five Mg2+ and one Cr2+ atom to form OMg5Cr octahedra that share corners with six OMg5Fe octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. Both O–Mg bond lengths are 2.12 Å. In the ninth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the tenth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg5Cr octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the eleventh O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form a mixture of corner and edge-sharing OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are one shorter (2.10 Å) and two longer (2.12 Å) O–Mg bond lengths. In the twelfth O2- site, O2- is bonded to five Mg2+ and one Fe2+ atom to form a mixture of corner and edge-sharing OMg5Fe octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of O–Mg bond distances ranging from 2.10–2.14 Å.

36 MATERIALS SCIENCE↗