Materials Data on CaMg2 by Materials Project

Abstract

Mg2Ca crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ca is bonded to six equivalent Ca and six Mg atoms to form distorted CaCa6Mg6 cuboctahedra that share corners with six equivalent CaCa6Mg6 cuboctahedra, corners with twelve MgCa4Mg8 cuboctahedra, edges with four equivalent CaCa6Mg6 cuboctahedra, edges with fourteen MgCa4Mg8 cuboctahedra, faces with eight equivalent CaCa6Mg6 cuboctahedra, and faces with twelve MgCa4Mg8 cuboctahedra. There are two shorter (3.44 Å) and four longer (3.54 Å) Ca–Ca bond lengths. There are a spread of Ca–Mg bond distances ranging from 3.42–3.68 Å. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded to four equivalent Ca and eight Mg atoms to form distorted MgCa4Mg8 cuboctahedra that share corners with six equivalent CaCa6Mg6 cuboctahedra, corners with twelve MgCa4Mg8 cuboctahedra, edges with three equivalent CaCa6Mg6 cuboctahedra, edges with fifteen MgCa4Mg8 cuboctahedra, faces with eight equivalent CaCa6Mg6 cuboctahedra, and faces with twelve MgCa4Mg8 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.22–3.46 Å. In the second Mg site, Mg is bonded to two equivalent Ca and ten Mg atoms to form distorted MgCa2Mg10 cuboctahedra that share corners with six equivalent CaCa6Mg6 cuboctahedra, corners with twelve MgCa4Mg8 cuboctahedra, edges with seven equivalent MgCa4Mg8 cuboctahedra, edges with eleven equivalent CaCa6Mg6 cuboctahedra, faces with four equivalent CaCa6Mg6 cuboctahedra, and faces with sixteen MgCa4Mg8 cuboctahedra. There are two shorter (3.27 Å) and two longer (3.44 Å) Mg–Mg bond lengths.