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DOE OSTI2020

Materials Data on MgCrO4 by Materials Project

MgCrO4 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six equivalent CrO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are two shorter (2.09 Å) and four longer (2.14 Å) Mg–O bond lengths. Cr6+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six equivalent MgO6 octahedra. The corner-sharing octahedra tilt angles range from 46–53°. There is two shorter (1.63 Å) and two longer (1.70 Å) Cr–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one Cr6+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mg2+ and one Cr6+ atom.

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DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

MgCr2O4 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 CrO6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Mg–O bond lengths are 2.00 Å. Cr3+ is bonded to six equivalent O2- atoms to form CrO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six equivalent CrO6 octahedra. All Cr–O bond lengths are 2.03 Å. O2- is bonded to one Mg2+ and three equivalent Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMgCr3 trigonal pyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

MgCr2O4 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 CrO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four equivalent CrO6 octahedra. There are two shorter (2.08 Å) and four longer (2.10 Å) Mg–O bond lengths. There are two inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six equivalent MgO6 octahedra and corners with six equivalent CrO6 octahedra. The corner-sharing octahedra tilt angles range from 53–66°. There is two shorter (1.91 Å) and two longer (2.00 Å) Cr–O bond length. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six equivalent CrO4 tetrahedra, edges with two equivalent CrO6 octahedra, and edges with four equivalent MgO6 octahedra. All Cr–O bond lengths are 2.03 Å. 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 Cr3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

MgCr2O4 crystallizes in the orthorhombic Pmmn 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 distorted MgO6 pentagonal pyramids that share corners with six equivalent CrO6 octahedra, edges with six CrO6 octahedra, and edges with two equivalent MgO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 4–16°. There are two shorter (2.07 Å) and four longer (2.27 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 pentagonal pyramids that share corners with twelve CrO6 octahedra, edges with two equivalent MgO6 pentagonal pyramids, and faces with two equivalent CrO6 octahedra. The corner-sharing octahedra tilt angles range from 44–54°. There are two shorter (2.10 Å) and four longer (2.26 Å) Mg–O bond lengths. 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 five MgO6 pentagonal pyramids, edges with six CrO6 octahedra, an edgeedge with one MgO6 pentagonal pyramid, and a faceface with one MgO6 pentagonal pyramid. There are a spread of Cr–O bond distances ranging from 1.99–2.10 Å. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent MgO6 pentagonal pyramids, edges with six CrO6 octahedra, and edges with two equivalent MgO6 pentagonal pyramids. There are a spread of Cr–O bond distances ranging from 1.98–2.05 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the second O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form OMgCr3 trigonal pyramids that share corners with four equivalent OMg2Cr3 trigonal bipyramids, corners with three equivalent OMgCr3 trigonal pyramids, and edges with four equivalent OMg2Cr3 trigonal bipyramids. In the third O2- site, O2- is bonded to two Mg2+ and three Cr3+ atoms to form OMg2Cr3 trigonal bipyramids that share corners with five equivalent OMg2Cr3 trigonal bipyramids, corners with two equivalent OMgCr3 trigonal pyramids, edges with four equivalent OMg2Cr3 trigonal bipyramids, and edges with two equivalent OMgCr3 trigonal pyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr4O8 by Materials Project

MgCr4O8 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Mg2+ is bonded to five O2- atoms to form MgO5 square pyramids that share corners with six CrO6 octahedra, edges with three CrO6 octahedra, edges with two equivalent MgO5 square pyramids, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 5–56°. There are a spread of Mg–O bond distances ranging from 2.07–2.10 Å. There are four inequivalent Cr+3.50+ sites. In the first Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four CrO6 octahedra, edges with four CrO6 octahedra, and edges with two equivalent MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 48–52°. There are a spread of Cr–O bond distances ranging from 1.92–2.16 Å. In the second Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form distorted CrO6 octahedra that share corners with four CrO6 octahedra, corners with two equivalent MgO5 square pyramids, edges with four CrO6 octahedra, and a faceface with one MgO5 square pyramid. The corner-sharing octahedra tilt angles range from 48–55°. There are a spread of Cr–O bond distances ranging from 1.88–2.18 Å. In the third Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four CrO6 octahedra, corners with two equivalent MgO5 square pyramids, and edges with four CrO6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of Cr–O bond distances ranging from 1.92–2.04 Å. In the fourth Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four CrO6 octahedra, corners with two equivalent MgO5 square pyramids, edges with four CrO6 octahedra, and an edgeedge with one MgO5 square pyramid. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Cr–O bond distances ranging from 1.92–2.11 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Cr+3.50+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Cr+3.50+ atoms. In the third O2- site, O2- is bonded in a trigonal planar geometry to three Cr+3.50+ atoms. In the fourth O2- site, O2- is bonded to one Mg2+ and three Cr+3.50+ atoms to form OMgCr3 trigonal pyramids that share corners with two equivalent OMgCr3 trigonal pyramids, edges with two equivalent OMg2Cr3 square pyramids, and edges with two equivalent OMg2Cr3 trigonal bipyramids. In the fifth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Cr+3.50+ atoms. In the sixth O2- site, O2- is bonded to two equivalent Mg2+ and three Cr+3.50+ atoms to form distorted OMg2Cr3 trigonal bipyramids that share corners with two equivalent OMg2Cr3 square pyramids, an edgeedge with one OMg2Cr3 square pyramid, edges with two equivalent OMg2Cr3 trigonal bipyramids, and edges with two equivalent OMgCr3 trigonal pyramids. In the seventh O2- site, O2- is bonded to two equivalent Mg2+ and three Cr+3.50+ atoms to form OMg2Cr3 square pyramids that share corners with two equivalent OMg2Cr3 trigonal bipyramids, edges with two equivalent OMg2Cr3 square pyramids, an edgeedge with one OMg2Cr3 trigonal bipyramid, and edges with two equivalent OMgCr3 trigonal pyramids. In the eighth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Cr+3.50+ atoms.

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DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

MgCr2O4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Mg2+ is bonded to five O2- atoms to form MgO5 square pyramids that share corners with six CrO6 octahedra, edges with three equivalent CrO6 octahedra, edges with two equivalent MgO5 square pyramids, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 7–59°. There are three shorter (2.06 Å) and two longer (2.08 Å) Mg–O bond lengths. 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 four equivalent CrO6 octahedra, corners with two equivalent MgO5 square pyramids, edges with four equivalent CrO6 octahedra, and edges with three equivalent MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Cr–O bond distances ranging from 1.95–2.21 Å. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent CrO6 octahedra, corners with four equivalent MgO5 square pyramids, edges with four equivalent CrO6 octahedra, and a faceface with one MgO5 square pyramid. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Cr–O bond distances ranging from 1.95–2.17 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form OMgCr3 trigonal pyramids that share corners with two equivalent OMg2Cr3 square pyramids, a cornercorner with one OMg2Cr3 trigonal bipyramid, corners with two equivalent OMgCr3 trigonal pyramids, edges with three equivalent OMg2Cr3 square pyramids, and edges with two equivalent OMg2Cr3 trigonal bipyramids. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Cr3+ atoms. In the third O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Cr3+ atoms to form OMg2Cr3 square pyramids that share corners with two equivalent OMg2Cr3 trigonal bipyramids, corners with two equivalent OMgCr3 trigonal pyramids, edges with four equivalent OMg2Cr3 square pyramids, an edgeedge with one OMg2Cr3 trigonal bipyramid, and edges with three equivalent OMgCr3 trigonal pyramids. In the fourth O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Cr3+ atoms to form distorted OMg2Cr3 trigonal bipyramids that share corners with two equivalent OMg2Cr3 square pyramids, a cornercorner with one OMgCr3 trigonal pyramid, an edgeedge with one OMg2Cr3 square pyramid, edges with four equivalent OMg2Cr3 trigonal bipyramids, and edges with two equivalent OMgCr3 trigonal pyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCrO2 by Materials Project

MgCrO2 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 five O2- atoms to form distorted MgO5 trigonal bipyramids that share corners with four equivalent CrO6 octahedra, edges with two equivalent MgO5 trigonal bipyramids, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 44–52°. There are a spread of Mg–O bond distances ranging from 2.08–2.21 Å. In the second Mg2+ site, Mg2+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are one shorter (2.04 Å) and two longer (2.06 Å) Mg–O bond lengths. There are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.00 Å) and two longer (2.12 Å) Cr–O bond lengths. In the second Cr2+ site, Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent MgO5 trigonal bipyramids, edges with four equivalent CrO6 octahedra, and a faceface with one MgO5 trigonal bipyramid. There are a spread of Cr–O bond distances ranging from 1.99–2.09 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Cr2+ atoms to form distorted OMgCr3 tetrahedra that share corners with two equivalent OMgCr3 tetrahedra, corners with four equivalent OMg3Cr2 trigonal bipyramids, and an edgeedge with one OMg3Cr2 trigonal bipyramid. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg2+ and two equivalent Cr2+ atoms. In the third O2- site, O2- is bonded to three Mg2+ and two equivalent Cr2+ atoms to form distorted OMg3Cr2 trigonal bipyramids that share corners with four equivalent OMgCr3 tetrahedra, an edgeedge with one OMgCr3 tetrahedra, and edges with two equivalent OMg3Cr2 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Mg2+ and three equivalent Cr2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Mg2Cr3O8 by Materials Project

Mg2Cr3O8 is beta indium sulfide-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.10–2.24 Å. There are two inequivalent Cr4+ sites. In the first Cr4+ site, Cr4+ is bonded to six O2- atoms to form edge-sharing CrO6 octahedra. There is four shorter (1.92 Å) and two longer (1.99 Å) Cr–O bond length. In the second Cr4+ site, Cr4+ is bonded to six O2- atoms to form edge-sharing CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.89–2.01 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two equivalent Cr4+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr4+ atoms. In the third O2- site, O2- is bonded to two equivalent Mg2+ and two Cr4+ atoms to form a mixture of distorted corner and edge-sharing OMg2Cr2 trigonal pyramids.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCrO2 by Materials Project

MgCrO2 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 five O2- atoms to form MgO5 trigonal bipyramids that share corners with four equivalent MgO4 tetrahedra, corners with two equivalent CrO5 trigonal bipyramids, edges with two equivalent MgO5 trigonal bipyramids, and a faceface with one CrO5 trigonal bipyramid. There are a spread of Mg–O bond distances ranging from 1.99–2.13 Å. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO4 tetrahedra, corners with four equivalent MgO5 trigonal bipyramids, corners with four equivalent CrO5 trigonal bipyramids, and an edgeedge with one CrO5 trigonal bipyramid. All Mg–O bond lengths are 1.98 Å. There are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are two shorter (1.98 Å) and two longer (2.19 Å) Cr–O bond lengths. In the second Cr2+ site, Cr2+ is bonded to five O2- atoms to form distorted CrO5 trigonal bipyramids that share corners with four equivalent MgO4 tetrahedra, corners with two equivalent MgO5 trigonal bipyramids, an edgeedge with one MgO4 tetrahedra, edges with two equivalent CrO5 trigonal bipyramids, and a faceface with one MgO5 trigonal bipyramid. There are a spread of Cr–O bond distances ranging from 2.09–2.30 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three Cr2+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two equivalent Cr2+ atoms. In the third O2- site, O2- is bonded to three Mg2+ and two equivalent Cr2+ atoms to form distorted edge-sharing OMg3Cr2 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to three Mg2+ and two equivalent Cr2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Mg2Cr2O5 by Materials Project

Mg2Cr2O5 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.08–2.50 Å. Cr3+ is bonded to five O2- atoms to form corner-sharing CrO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.93–2.00 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Mg2+ and two equivalent Cr3+ atoms to form distorted OMg4Cr2 octahedra that share corners with eight equivalent OMg2Cr2 tetrahedra, corners with four equivalent OMg2Cr2 trigonal pyramids, edges with two equivalent OMg4Cr2 octahedra, edges with two equivalent OMg2Cr2 tetrahedra, and edges with four equivalent OMg2Cr2 trigonal pyramids. In the second O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Cr3+ atoms to form distorted OMg2Cr2 tetrahedra that share corners with four equivalent OMg4Cr2 octahedra, corners with four equivalent OMg2Cr2 tetrahedra, corners with four equivalent OMg2Cr2 trigonal pyramids, an edgeedge with one OMg4Cr2 octahedra, and edges with two equivalent OMg2Cr2 trigonal pyramids. The corner-sharing octahedra tilt angles range from 18–60°. In the third O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Cr3+ atoms to form distorted OMg2Cr2 trigonal pyramids that share corners with two equivalent OMg4Cr2 octahedra, corners with four equivalent OMg2Cr2 tetrahedra, corners with two equivalent OMg2Cr2 trigonal pyramids, edges with two equivalent OMg4Cr2 octahedra, edges with two equivalent OMg2Cr2 tetrahedra, and an edgeedge with one OMg2Cr2 trigonal pyramid. The corner-sharing octahedral tilt angles are 58°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCrO3 by Materials Project

MgCrO3 is Orthorhombic Perovskite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded in a 4-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.04–2.60 Å. Cr4+ is bonded to six O2- atoms to form corner-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Cr–O bond distances ranging from 1.93–1.97 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Cr4+ atoms to form distorted corner-sharing OMg2Cr2 trigonal pyramids. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Mg2+ and two equivalent Cr4+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCrO2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

MgCr2O4 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 MgO6 octahedra and corners with nine CrO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Mg–O bond distances ranging from 1.97–2.05 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three CrO4 tetrahedra, and edges with six CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.13 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 CrO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Mg–O bond distances ranging from 1.97–2.05 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four CrO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.13 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent CrO6 octahedra. There are four shorter (2.09 Å) and two longer (2.11 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.12 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five CrO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.13 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.12 Å. There are twelve inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with three MgO4 tetrahedra, corners with three CrO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.99–2.06 Å. In the second 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 CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.99–2.07 Å. In the third Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 54–62°. There are a spread of Cr–O bond distances ranging from 1.91–2.01 Å. In the fourth Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four CrO4 tetrahedra, edges with three MgO6 octahedra, and edges with three CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.99–2.04 Å. In the fifth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CrO6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are a spread of Cr–O bond distances ranging from 1.92–2.08 Å. In the sixth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 54–63°. There are a spread of Cr–O bond distances ranging from 1.91–2.00 Å. In the seventh Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six CrO4 tetrahedra, edges with two equivalent CrO6 octahedra, and edges with four MgO6 octahedra. There are one shorter (2.02 Å) and five longer (2.03 Å) Cr–O bond lengths. In the eighth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 55–62°. There are a spread of Cr–O bond distances ranging from 1.91–2.00 Å. In the ninth Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five CrO4 tetrahedra, edges with three MgO6 octahedra, and edges with three CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.01–2.04 Å. In the tenth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There is two shorter (1.91 Å) and two longer (1.99 Å) Cr–O bond length. In the eleventh 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 CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.00–2.06 Å. In the twelfth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CrO6 octahedra. The corner-sharing octahedra tilt angles range from 57–60°. There are a spread of Cr–O bond distances ranging from 1.92–2.08 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Mg2+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMg2Cr2 trigonal pyramids. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Cr3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Cr3+ atoms. In the fifth O2- site, O2- is bonded to two Mg2+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMg2Cr2 trigonal pyramids. In the sixth O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form distorted OMgCr3 trigonal pyramids that share corners with six OMg2Cr2 trigonal pyramids and an edgeedge with one OMgCr3 trigonal pyramid. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the tenth O2- site, O2- is bonded to two Mg2+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMg2Cr2 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the twelfth O2- site, O2- is bonded to two Mg2+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OMg2Cr2 trigonal pyramids. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the nineteenth O2- site, O2- is bonded to two Mg2+ and two equivalent Cr3+ atoms to form distorted corner-sharing OMg2Cr2 trigonal pyramids. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the twenty-second O2- site, O2- is bonded to four Cr3+ atoms to form distorted OCr4 trigonal pyramids that share corners with six OMg2Cr2 trigonal pyramids and edges with two equivalent OMgCr3 trigonal pyramids. In the twenty-third O2- site, O2- is bonded to one Mg2+ and three Cr3+ atoms to form distorted OMgCr3 trigonal pyramids that share corners with six OMg2Cr2 trigonal pyramids and edges with two OCr4 trigonal pyramids. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

MgCr2O4 is Spinel-like structured and crystallizes in the monoclinic Cm 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 MgO6 octahedra and corners with nine CrO6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are a spread of Mg–O bond distances ranging from 1.97–2.03 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.11 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four CrO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.12 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.11 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent CrO6 octahedra. There are three shorter (2.09 Å) and three longer (2.10 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five CrO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five CrO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.12 Å. There are nine 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 CrO4 tetrahedra, edges with three MgO6 octahedra, and edges with three CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.99–2.04 Å. In the second Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 53–65°. There are a spread of Cr–O bond distances ranging from 1.91–1.99 Å. In the third 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 CrO4 tetrahedra, edges with two MgO6 octahedra, and edges with four CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.98–2.05 Å. In the fourth Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six CrO4 tetrahedra, edges with two equivalent CrO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.02–2.04 Å. In the fifth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 53–66°. There are a spread of Cr–O bond distances ranging from 1.91–2.00 Å. In the sixth Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five CrO4 tetrahedra, edges with three MgO6 octahedra, and edges with three CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.01–2.04 Å. In the seventh Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 54–64°. There is two shorter (1.90 Å) and two longer (1.99 Å) Cr–O bond length. In the eighth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with six MgO6 octahedra and corners with six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 54–65°. There are a spread of Cr–O bond distances ranging from 1.91–2.00 Å. In the ninth Cr3+ site, Cr3+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine CrO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Cr–O bond distances ranging from 1.93–2.04 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Cr3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Cr3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Cr3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Cr3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr2O7 by Materials Project

MgCr2O7 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share corners with five CrO4 tetrahedra and corners with two equivalent MgO5 trigonal bipyramids. There are a spread of Mg–O bond distances ranging from 2.02–2.36 Å. There are two inequivalent Cr6+ sites. In the first Cr6+ site, Cr6+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one CrO4 tetrahedra and corners with three equivalent MgO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.59–1.76 Å. In the second Cr6+ site, Cr6+ is bonded to four O2- atoms to form CrO4 tetrahedra that share a cornercorner with one CrO4 tetrahedra and corners with two equivalent MgO5 trigonal bipyramids. There are a spread of Cr–O bond distances ranging from 1.59–1.81 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one Cr6+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Mg2+ and one Cr6+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mg2+ and one Cr6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mg2+ and one Cr6+ atom. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two Cr6+ atoms. In the seventh O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCr2O4 by Materials Project

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MgCrO4 by Materials Project

36 MATERIALS SCIENCE↗