DOI: 10.17188/1672005
title: Materials Data on Mg6NbCoO8 by Materials Project

description: Mg6NbCoO8 is Caswellsilverite-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 six MgO6 octahedra, edges with four equivalent CoO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.14 Å) and two longer (2.23 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 six MgO6 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 (2.14 Å) and two longer (2.19 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 CoO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Mg–O bond distances ranging from 2.06–2.36 Å. Nb2+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent CoO6 octahedra, corners with four equivalent NbO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.14 Å) and two longer (2.16 Å) Nb–O bond lengths. Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four equivalent CoO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.14 Å) and two longer (2.25 Å) Co–O bond lengths. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Mg2+, one Nb2+, and one Co2+ atom to form OMg4NbCo octahedra that share corners with six equivalent OMg4NbCo octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–11°. In the second O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg4NbCo octahedra. The corner-sharing octahedra tilt angles range from 0–9°. In the third O2- site, O2- is bonded to four Mg2+ and two equivalent Co2+ atoms to form OMg4Co2 octahedra that share corners with six OMg4Co2 octahedra and edges with twelve OMg4NbCo octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to four Mg2+ and two equivalent Nb2+ atoms to form OMg4Nb2 octahedra that share corners with six OMg4Co2 octahedra and edges with twelve OMg4NbCo octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to four Mg2+ and two equivalent Co2+ atoms to form OMg4Co2 octahedra that share corners with six OMg4Nb2 octahedra and edges with twelve OMg4NbCo octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.06 Å.