Materials Data on Ca3Mg by Materials Project

Abstract

MgCa3 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are three inequivalent Ca sites. In the first Ca site, Ca is bonded to ten Ca and two equivalent Mg atoms to form a mixture of distorted face, edge, and corner-sharing CaCa10Mg2 cuboctahedra. There are a spread of Ca–Ca bond distances ranging from 3.66–3.79 Å. Both Ca–Mg bond lengths are 3.68 Å. In the second Ca site, Ca is bonded to eight Ca and four equivalent Mg atoms to form a mixture of distorted face, edge, and corner-sharing CaCa8Mg4 cuboctahedra. There are two shorter (3.73 Å) and two longer (3.78 Å) Ca–Ca bond lengths. All Ca–Mg bond lengths are 3.71 Å. In the third Ca site, Ca is bonded to eight Ca and four equivalent Mg atoms to form distorted CaCa8Mg4 cuboctahedra that share corners with ten equivalent CaCa8Mg4 cuboctahedra, edges with fourteen CaCa10Mg2 cuboctahedra, and faces with sixteen CaCa10Mg2 cuboctahedra. Both Ca–Ca bond lengths are 3.78 Å. There are two shorter (3.72 Å) and two longer (3.73 Å) Ca–Mg bond lengths. Mg is bonded in a distorted q6 geometry to ten Ca atoms.