Materials Data on Ba3(AlAs2)2 by Materials Project

Abstract

Ba3Al2As4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to six As3- atoms to form distorted BaAs6 pentagonal pyramids that share corners with four equivalent BaAs6 octahedra, corners with four equivalent BaAs6 pentagonal pyramids, corners with six equivalent AlAs4 tetrahedra, edges with two equivalent BaAs6 octahedra, edges with three equivalent BaAs6 pentagonal pyramids, edges with three equivalent AlAs4 tetrahedra, and a faceface with one BaAs6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 38–89°. There are a spread of Ba–As bond distances ranging from 3.25–3.61 Å. In the second Ba2+ site, Ba2+ is bonded to six As3- atoms to form BaAs6 octahedra that share corners with eight equivalent BaAs6 pentagonal pyramids, corners with eight equivalent AlAs4 tetrahedra, edges with four equivalent BaAs6 pentagonal pyramids, edges with two equivalent AlAs4 tetrahedra, and faces with two equivalent BaAs6 octahedra. There are a spread of Ba–As bond distances ranging from 3.26–3.47 Å. Al3+ is bonded to four As3- atoms to form AlAs4 tetrahedra that share corners with four equivalent BaAs6 octahedra, corners with six equivalent BaAs6 pentagonal pyramids, an edgeedge with one BaAs6 octahedra, edges with three equivalent BaAs6 pentagonal pyramids, and edges with two equivalent AlAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–62°. There are a spread of Al–As bond distances ranging from 2.50–2.57 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 6-coordinate geometry to four equivalent Ba2+ and two equivalent Al3+ atoms. In the second As3- site, As3- is bonded in a 7-coordinate geometry to five Ba2+ and two equivalent Al3+ atoms. In the third As3- site, As3- is bonded in a 6-coordinate geometry to four Ba2+ and two equivalent Al3+ atoms.