DOI: 10.17188/1652252
title: Materials Data on Mg6NbCrO8 by Materials Project

description: Mg6NbCrO8 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.13 Å) and four longer (2.15 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.08 Å) and four longer (2.15 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six equivalent MgO6 octahedra, edges with two equivalent NbO6 octahedra, edges with two equivalent CrO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Mg–O bond distances ranging from 2.13–2.31 Å. Nb2+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent NbO6 octahedra, edges with four equivalent CrO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.15 Å) and two longer (2.32 Å) Nb–O bond lengths. Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent CrO6 octahedra, edges with four equivalent NbO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.15 Å) and two longer (2.37 Å) Cr–O bond lengths. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form OMg5Nb octahedra that share corners with six equivalent OMg5Nb octahedra and edges with twelve OMg5Cr octahedra. The corner-sharing octahedral tilt angles are 0°. In the second O2- site, O2- is bonded to five Mg2+ and one Cr2+ atom to form OMg5Cr octahedra that share corners with six equivalent OMg5Cr octahedra and edges with twelve OMg5Nb octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the third O2- site, O2- is bonded to two equivalent Mg2+, two equivalent Nb2+, and two equivalent Cr2+ atoms to form OMg2Nb2Cr2 octahedra that share corners with six OMg2Nb2Cr2 octahedra and edges with twelve OMg5Nb octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg2Nb2Cr2 octahedra and edges with twelve OMg5Nb octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to two equivalent Mg2+, two equivalent Nb2+, and two equivalent Cr2+ atoms to form OMg2Nb2Cr2 octahedra that share corners with six OMg6 octahedra and edges with twelve OMg5Nb octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.31 Å.