Materials Data on CaMg2 by Materials Project

Abstract

Mg2Ca crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded to six equivalent Ca and six Mg atoms to form CaCa6Mg6 cuboctahedra that share corners with six equivalent MgMg12 cuboctahedra, corners with twelve CaCa6Mg6 cuboctahedra, edges with six equivalent CaCa6Mg6 cuboctahedra, edges with twelve MgCa3Mg9 cuboctahedra, faces with seven CaCa6Mg6 cuboctahedra, and faces with thirteen MgMg12 cuboctahedra. All Ca–Ca bond lengths are 3.48 Å. All Ca–Mg bond lengths are 3.51 Å. In the second Ca site, Ca is bonded to six equivalent Ca and six Mg atoms to form CaCa6Mg6 cuboctahedra that share corners with six equivalent MgMg12 cuboctahedra, corners with twelve CaCa6Mg6 cuboctahedra, edges with six equivalent CaCa6Mg6 cuboctahedra, edges with twelve MgCa3Mg9 cuboctahedra, faces with seven CaCa6Mg6 cuboctahedra, and faces with thirteen MgMg12 cuboctahedra. All Ca–Ca bond lengths are 3.48 Å. All Ca–Mg bond lengths are 3.51 Å. There are three inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with six equivalent MgMg12 cuboctahedra, corners with twelve CaCa6Mg6 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, faces with two CaCa6Mg6 cuboctahedra, and faces with eighteen MgMg12 cuboctahedra. There are six shorter (3.28 Å) and six longer (3.48 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to three equivalent Ca and nine Mg atoms to form distorted MgCa3Mg9 cuboctahedra that share corners with eighteen MgCa3Mg9 cuboctahedra, edges with six equivalent CaCa6Mg6 cuboctahedra, edges with twelve MgMg12 cuboctahedra, faces with six equivalent CaCa6Mg6 cuboctahedra, and faces with fourteen MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.48 Å. In the third Mg site, Mg is bonded to six Ca and six equivalent Mg atoms to form distorted MgCa6Mg6 cuboctahedra that share corners with eighteen MgCa3Mg9 cuboctahedra, edges with six equivalent MgCa6Mg6 cuboctahedra, edges with twelve CaCa6Mg6 cuboctahedra, faces with eight MgCa3Mg9 cuboctahedra, and faces with twelve CaCa6Mg6 cuboctahedra. All Mg–Mg bond lengths are 3.48 Å.