DOI: 10.17188/1321225
title: Materials Data on MgCr2O4 by Materials Project

description: 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.