DOI: 10.17188/1652623
title: Materials Data on RbMg6CO8 by Materials Project

description: RbMg6CO8 is Caswellsilverite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Rb1+ is bonded to six O2- atoms to form RbO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent RbO6 octahedra, edges with four equivalent CO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.19 Å) and two longer (2.52 Å) Rb–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 two equivalent RbO6 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 (1.98 Å) and four longer (2.19 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 CO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.19 Å) and two longer (2.24 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 RbO6 octahedra, edges with two equivalent CO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. There are a spread of Mg–O bond distances ranging from 2.14–2.36 Å. C3+ is bonded to six O2- atoms to form CO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent CO6 octahedra, edges with four equivalent RbO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.19 Å) and two longer (2.26 Å) C–O bond lengths. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded to one Rb1+ and five Mg2+ atoms to form ORbMg5 octahedra that share corners with six equivalent ORbMg5 octahedra and edges with twelve OMg5C octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the second O2- site, O2- is bonded to five Mg2+ and one C3+ atom to form distorted OMg5C octahedra that share corners with six equivalent OMg5C octahedra and edges with twelve ORbMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the third O2- site, O2- is bonded to two equivalent Rb1+, two equivalent Mg2+, and two equivalent C3+ atoms to form ORb2Mg2C2 octahedra that share corners with six ORb2Mg2C2 octahedra and edges with twelve ORbMg5 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 ORb2Mg2C2 octahedra and edges with twelve ORbMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to two equivalent Rb1+, two equivalent Mg2+, and two equivalent C3+ atoms to form ORb2Mg2C2 octahedra that share corners with six ORb2Mg2C2 octahedra and edges with twelve ORbMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.36 Å. In the sixth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six ORb2Mg2C2 octahedra and edges with twelve ORbMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.14 Å.