DOI: 10.17188/1654302
title: Materials Data on CaMg6CO8 by Materials Project

description: CaMg6CO8 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent CO6 octahedra, corners with four equivalent CaO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.17 Å) and two longer (2.28 Å) Ca–O bond lengths. 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 CaO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Mg–O bond lengths are 2.17 Å. 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 CO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.13 Å) and four longer (2.17 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 CaO6 octahedra, edges with two equivalent CO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.06–2.24 Å. C2+ is bonded to six O2- atoms to form CO6 octahedra that share corners with two equivalent CaO6 octahedra, corners with four equivalent CO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.02 Å) and four longer (2.17 Å) C–O bond lengths. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded to one Ca2+, four equivalent Mg2+, and one C2+ atom to form OCaMg4C octahedra that share corners with six equivalent OCaMg4C octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. 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 OCaMg4C octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the third O2- site, O2- is bonded to two equivalent Ca2+ and four Mg2+ atoms to form OCa2Mg4 octahedra that share corners with six OCa2Mg4 octahedra and edges with twelve OCaMg4C octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to four Mg2+ and two equivalent C2+ atoms to form OMg4C2 octahedra that share corners with six OCa2Mg4 octahedra and edges with twelve OCaMg4C octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to two equivalent Ca2+ and four Mg2+ atoms to form OCa2Mg4 octahedra that share corners with six OCa2Mg4 octahedra and edges with twelve OCaMg4C octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.24 Å. In the sixth O2- site, O2- is bonded to four Mg2+ and two equivalent C2+ atoms to form OMg4C2 octahedra that share corners with six OCa2Mg4 octahedra and edges with twelve OCaMg4C octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.06 Å.