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.