Materials Data on Ca(MgAs)2 by Materials Project

Abstract

Ca(MgAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent As3- atoms to form CaAs6 octahedra that share corners with twelve equivalent MgAs4 tetrahedra, edges with six equivalent CaAs6 octahedra, and edges with six equivalent MgAs4 tetrahedra. All Ca–As bond lengths are 3.09 Å. Mg2+ is bonded to four equivalent As3- atoms to form MgAs4 tetrahedra that share corners with six equivalent CaAs6 octahedra, corners with six equivalent MgAs4 tetrahedra, edges with three equivalent CaAs6 octahedra, and edges with three equivalent MgAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 17–55°. There are three shorter (2.66 Å) and one longer (2.75 Å) Mg–As bond lengths. As3- is bonded to three equivalent Ca2+ and four equivalent Mg2+ atoms to form a mixture of distorted edge and corner-sharing AsCa3Mg4 pentagonal bipyramids.