Materials Data on Ca5(SnAs3)2 by Materials Project

Abstract

Ca5(SnAs3)2 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six As3- atoms to form CaAs6 octahedra that share corners with five CaAs6 octahedra, corners with six equivalent CaAs7 pentagonal bipyramids, corners with four equivalent SnAs4 tetrahedra, edges with two equivalent CaAs6 octahedra, an edgeedge with one CaAs7 pentagonal bipyramid, edges with two equivalent SnAs4 tetrahedra, a faceface with one CaAs6 octahedra, and faces with two equivalent CaAs7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 22–52°. There are a spread of Ca–As bond distances ranging from 3.02–3.17 Å. In the second Ca2+ site, Ca2+ is bonded to six As3- atoms to form CaAs6 octahedra that share corners with six equivalent CaAs6 octahedra, corners with six equivalent CaAs7 pentagonal bipyramids, edges with two equivalent CaAs6 octahedra, edges with two equivalent CaAs7 pentagonal bipyramids, edges with four equivalent SnAs4 tetrahedra, and faces with two equivalent CaAs6 octahedra. The corner-sharing octahedra tilt angles range from 50–52°. There are four shorter (3.11 Å) and two longer (3.14 Å) Ca–As bond lengths. In the third Ca2+ site, Ca2+ is bonded to seven As3- atoms to form distorted CaAs7 pentagonal bipyramids that share corners with nine CaAs6 octahedra, corners with four equivalent SnAs4 tetrahedra, edges with two CaAs6 octahedra, edges with two equivalent CaAs7 pentagonal bipyramids, edges with two equivalent SnAs4 tetrahedra, faces with two equivalent CaAs6 octahedra, and faces with three equivalent CaAs7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 25–51°. There are a spread of Ca–As bond distances ranging from 3.09–3.33 Å. Sn4+ is bonded to four As3- atoms to form SnAs4 tetrahedra that share corners with four equivalent CaAs6 octahedra, corners with four equivalent CaAs7 pentagonal bipyramids, corners with two equivalent SnAs4 tetrahedra, edges with four CaAs6 octahedra, and edges with two equivalent CaAs7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 43–62°. There are two shorter (2.65 Å) and two longer (2.68 Å) Sn–As bond lengths. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 6-coordinate geometry to four Ca2+ and two equivalent Sn4+ atoms. In the second As3- site, As3- is bonded to six Ca2+ and one Sn4+ atom to form a mixture of distorted corner, edge, and face-sharing AsCa6Sn pentagonal bipyramids. In the third As3- site, As3- is bonded in a 7-coordinate geometry to six Ca2+ and one Sn4+ atom.