Materials Data on CaMg2 by Materials Project

Abstract

Mg2Ca crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Ca is bonded to three equivalent Ca and nine Mg atoms to form CaCa3Mg9 cuboctahedra that share corners with nine equivalent CaCa3Mg9 cuboctahedra, corners with nine equivalent MgCa6Mg6 cuboctahedra, edges with six equivalent CaCa3Mg9 cuboctahedra, faces with three equivalent MgCa6Mg6 cuboctahedra, and faces with five equivalent CaCa3Mg9 cuboctahedra. All Ca–Ca bond lengths are 3.47 Å. There are six shorter (3.46 Å) and three longer (3.47 Å) Ca–Mg bond lengths. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to four equivalent Ca and four Mg atoms. There are two shorter (3.21 Å) and two longer (3.33 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to six equivalent Ca and six equivalent Mg atoms to form MgCa6Mg6 cuboctahedra that share corners with eighteen equivalent CaCa3Mg9 cuboctahedra, edges with six equivalent MgCa6Mg6 cuboctahedra, faces with two equivalent MgCa6Mg6 cuboctahedra, and faces with six equivalent CaCa3Mg9 cuboctahedra.