Materials Data on Ca3(AlAs2)2 by Materials Project

Abstract

Ca3Al2As4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six As3- atoms to form CaAs6 octahedra that share corners with ten equivalent CaAs6 octahedra, corners with four equivalent AlAs4 tetrahedra, edges with two equivalent CaAs6 octahedra, edges with four equivalent AlAs4 tetrahedra, and faces with two equivalent CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 36–58°. There are a spread of Ca–As bond distances ranging from 2.92–3.14 Å. In the second Ca2+ site, Ca2+ is bonded to six As3- atoms to form distorted CaAs6 octahedra that share corners with seven CaAs6 octahedra, corners with six equivalent AlAs4 tetrahedra, edges with six equivalent CaAs6 octahedra, edges with three equivalent AlAs4 tetrahedra, and a faceface with one CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 15–58°. There are a spread of Ca–As bond distances ranging from 2.93–3.40 Å. Al3+ is bonded to four As3- atoms to form AlAs4 tetrahedra that share corners with eight CaAs6 octahedra, corners with two equivalent AlAs4 tetrahedra, edges with five CaAs6 octahedra, and an edgeedge with one AlAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–83°. There are a spread of Al–As bond distances ranging from 2.46–2.53 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 6-coordinate geometry to four Ca2+ and two equivalent Al3+ atoms. In the second As3- site, As3- is bonded in a 7-coordinate geometry to five Ca2+ and two equivalent Al3+ atoms.