DOI: 10.17188/1319051
title: Materials Data on Mg(CoO2)2 by Materials Project

description: MgCo2O4 crystallizes in the triclinic P1 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 square pyramids that share corners with six CoO6 octahedra, edges with three CoO6 octahedra, edges with two equivalent MgO5 square pyramids, and a faceface with one CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–60°. There are two shorter (2.01 Å) and three longer (2.04 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 square pyramids that share corners with six CoO6 octahedra, edges with three CoO6 octahedra, edges with two equivalent MgO5 square pyramids, and a faceface with one CoO6 octahedra. The corner-sharing octahedra tilt angles range from 6–60°. There are a spread of Mg–O bond distances ranging from 2.01–2.04 Å. There are four inequivalent Co3+ sites. In the first Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four CoO6 octahedra, corners with two equivalent MgO5 square pyramids, edges with four CoO6 octahedra, and edges with three MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Co–O bond distances ranging from 1.85–2.13 Å. In the second Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four CoO6 octahedra, corners with four MgO5 square pyramids, edges with four CoO6 octahedra, and a faceface with one MgO5 square pyramid. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Co–O bond distances ranging from 1.88–2.01 Å. In the third Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four CoO6 octahedra, corners with four MgO5 square pyramids, edges with four CoO6 octahedra, and a faceface with one MgO5 square pyramid. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Co–O bond distances ranging from 1.88–2.01 Å. In the fourth Co3+ site, Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with four CoO6 octahedra, corners with two equivalent MgO5 square pyramids, edges with four CoO6 octahedra, and edges with three MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Co–O bond distances ranging from 1.84–2.12 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Co3+ atoms to form OMgCo3 trigonal pyramids that share corners with two equivalent OMg2Co3 square pyramids, a cornercorner with one OMg2Co3 trigonal bipyramid, corners with two equivalent OMgCo3 trigonal pyramids, edges with three OMg2Co3 square pyramids, and edges with two equivalent OMg2Co3 trigonal bipyramids. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Co3+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Co3+ atoms. In the fourth O2- site, O2- is bonded to one Mg2+ and three Co3+ atoms to form OMgCo3 trigonal pyramids that share corners with two equivalent OMg2Co3 square pyramids, a cornercorner with one OMg2Co3 trigonal bipyramid, corners with two equivalent OMgCo3 trigonal pyramids, edges with three OMg2Co3 square pyramids, and edges with two equivalent OMg2Co3 trigonal bipyramids. In the fifth O2- site, O2- is bonded to two equivalent Mg2+ and three Co3+ atoms to form OMg2Co3 square pyramids that share corners with two equivalent OMg2Co3 trigonal bipyramids, corners with two equivalent OMgCo3 trigonal pyramids, edges with four OMg2Co3 square pyramids, an edgeedge with one OMg2Co3 trigonal bipyramid, and edges with three OMgCo3 trigonal pyramids. In the sixth O2- site, O2- is bonded to two equivalent Mg2+ and three Co3+ atoms to form distorted OMg2Co3 trigonal bipyramids that share corners with two equivalent OMg2Co3 square pyramids, a cornercorner with one OMgCo3 trigonal pyramid, an edgeedge with one OMg2Co3 square pyramid, edges with four OMg2Co3 trigonal bipyramids, and edges with two equivalent OMgCo3 trigonal pyramids. In the seventh O2- site, O2- is bonded to two equivalent Mg2+ and three Co3+ atoms to form OMg2Co3 square pyramids that share corners with two equivalent OMg2Co3 trigonal bipyramids, corners with two equivalent OMgCo3 trigonal pyramids, edges with four OMg2Co3 square pyramids, an edgeedge with one OMg2Co3 trigonal bipyramid, and edges with three OMgCo3 trigonal pyramids. In the eighth O2- site, O2- is bonded to two equivalent Mg2+ and three Co3+ atoms to form distorted OMg2Co3 trigonal bipyramids that share corners with two equivalent OMg2Co3 square pyramids, a cornercorner with one OMgCo3 trigonal pyramid, an edgeedge with one OMg2Co3 square pyramid, edges with four OMg2Co3 trigonal bipyramids, and edges with two equivalent OMgCo3 trigonal pyramids.