Materials Data on Ca2Mg by Materials Project

Abstract

Ca2Mg crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Ca sites. In the first Ca site, Ca is bonded to nine Ca and three Mg atoms to form distorted CaCa9Mg3 cuboctahedra that share corners with twelve CaCa9Mg3 cuboctahedra, edges with five CaCa7Mg5 cuboctahedra, and faces with ten CaCa9Mg3 cuboctahedra. There are a spread of Ca–Ca bond distances ranging from 3.71–3.84 Å. There are two shorter (3.51 Å) and one longer (3.71 Å) Ca–Mg bond lengths. In the second Ca site, Ca is bonded to seven Ca and five Mg atoms to form a mixture of distorted edge, face, and corner-sharing CaCa7Mg5 cuboctahedra. There are two shorter (3.70 Å) and three longer (3.71 Å) Ca–Ca bond lengths. There are a spread of Ca–Mg bond distances ranging from 3.53–3.79 Å. In the third Ca site, Ca is bonded in a 12-coordinate geometry to six Ca and three Mg atoms. Both Ca–Ca bond lengths are 3.81 Å. There are one shorter (3.40 Å) and two longer (3.56 Å) Ca–Mg bond lengths. In the fourth Ca site, Ca is bonded to eight Ca and four Mg atoms to form distorted CaCa8Mg4 cuboctahedra that share corners with six equivalent CaCa8Mg4 cuboctahedra, edges with six CaCa9Mg3 cuboctahedra, and faces with eleven CaCa9Mg3 cuboctahedra. Both Ca–Ca bond lengths are 3.71 Å. There are two shorter (3.66 Å) and two longer (3.73 Å) Ca–Mg bond lengths. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 8-coordinate geometry to eight Ca atoms. In the second Mg site, Mg is bonded in a 7-coordinate geometry to seven Ca atoms.