Materials Data on CaMg2 by Materials Project

Abstract

Mg2Ca is beta-derived structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca is bonded to nine equivalent Ca and three equivalent Mg atoms to form distorted CaCa9Mg3 cuboctahedra that share corners with six equivalent CaCa9Mg3 cuboctahedra, corners with twelve MgCa3Mg9 cuboctahedra, edges with six equivalent MgCa3Mg9 cuboctahedra, edges with twelve equivalent CaCa9Mg3 cuboctahedra, faces with eight MgCa3Mg9 cuboctahedra, and faces with twelve equivalent CaCa9Mg3 cuboctahedra. There are six shorter (3.45 Å) and three longer (3.79 Å) Ca–Ca bond lengths. All Ca–Mg bond lengths are 3.50 Å. There are three inequivalent Mg sites. In the first Mg site, Mg is bonded to three equivalent Ca and nine Mg atoms to form distorted MgCa3Mg9 cuboctahedra that share corners with six equivalent CaCa9Mg3 cuboctahedra, corners with twelve MgCa3Mg9 cuboctahedra, edges with six equivalent CaCa9Mg3 cuboctahedra, edges with twelve MgCa3Mg9 cuboctahedra, faces with seven equivalent CaCa9Mg3 cuboctahedra, and faces with thirteen MgCa3Mg9 cuboctahedra. There are three shorter (3.30 Å) and six longer (3.45 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with six equivalent CaCa9Mg3 cuboctahedra, corners with twelve MgCa3Mg9 cuboctahedra, edges with eighteen MgCa3Mg9 cuboctahedra, a faceface with one CaCa9Mg3 cuboctahedra, and faces with nineteen MgCa3Mg9 cuboctahedra. There are three shorter (3.30 Å) and six longer (3.45 Å) Mg–Mg bond lengths. In the third Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with six equivalent CaCa9Mg3 cuboctahedra, corners with twelve MgCa3Mg9 cuboctahedra, edges with eighteen MgCa3Mg9 cuboctahedra, a faceface with one CaCa9Mg3 cuboctahedra, and faces with nineteen MgCa3Mg9 cuboctahedra. There are three shorter (3.30 Å) and six longer (3.45 Å) Mg–Mg bond lengths.