Materials Data on MgCr(GeO3)2 by Materials Project

Abstract

MgCr(GeO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GeO4 tetrahedra, edges with three equivalent CrO6 octahedra, and an edgeedge with one GeO4 tetrahedra. There are a spread of Mg–O bond distances ranging from 1.99–2.33 Å. Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six GeO4 tetrahedra, edges with two equivalent CrO6 octahedra, and edges with three equivalent MgO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.06–2.39 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent CrO6 octahedra, corners with four equivalent MgO6 octahedra, and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–65°. There are a spread of Ge–O bond distances ranging from 1.71–1.84 Å. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two equivalent MgO6 octahedra, corners with three equivalent CrO6 octahedra, corners with two equivalent GeO4 tetrahedra, and an edgeedge with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 30–64°. There are a spread of Ge–O bond distances ranging from 1.74–1.82 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+, two equivalent Cr2+, and one Ge4+ atom to form distorted corner-sharing OMgCr2Ge trigonal pyramids. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Cr2+, and one Ge4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent Ge4+ atoms. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to one Mg2+ and two equivalent Ge4+ atoms. In the fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Mg2+, one Cr2+, and one Ge4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Cr2+, and one Ge4+ atom.