Materials Data on MgCrO2 by Materials Project

Abstract

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.