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 two equivalent Ca and ten Mg atoms to form distorted CaCa2Mg10 cuboctahedra that share corners with six equivalent CaCa2Mg10 cuboctahedra, corners with twelve MgCa6Mg6 cuboctahedra, edges with eight equivalent CaCa2Mg10 cuboctahedra, edges with ten MgCa6Mg6 cuboctahedra, faces with six equivalent CaCa2Mg10 cuboctahedra, and faces with fourteen MgCa6Mg6 cuboctahedra. Both Ca–Ca bond lengths are 3.47 Å. There are a spread of Ca–Mg bond distances ranging from 3.39–3.48 Å. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded to six equivalent Ca and six Mg atoms to form distorted MgCa6Mg6 cuboctahedra that share corners with six equivalent CaCa2Mg10 cuboctahedra, corners with twelve MgCa6Mg6 cuboctahedra, edges with seven equivalent CaCa2Mg10 cuboctahedra, edges with eleven equivalent MgCa4Mg8 cuboctahedra, faces with six equivalent CaCa2Mg10 cuboctahedra, and faces with fourteen MgCa6Mg6 cuboctahedra. There are two shorter (3.32 Å) and four longer (3.47 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to four equivalent Ca and eight Mg atoms to form distorted MgCa4Mg8 cuboctahedra that share corners with six equivalent CaCa2Mg10 cuboctahedra, corners with twelve MgCa6Mg6 cuboctahedra, edges with three equivalent CaCa2Mg10 cuboctahedra, edges with fifteen MgCa6Mg6 cuboctahedra, faces with eight equivalent CaCa2Mg10 cuboctahedra, and faces with twelve MgCa6Mg6 cuboctahedra. All Mg–Mg bond lengths are 3.47 Å.