DOE OSTI2020
Sr5(SnP3)2 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to seven P3- atoms to form distorted SrP7 pentagonal bipyramids that share corners with nine SrP6 octahedra, corners with four equivalent SnP4 tetrahedra, edges with two SrP6 octahedra, edges with two equivalent SrP7 pentagonal bipyramids, edges with two equivalent SnP4 tetrahedra, faces with two equivalent SrP6 octahedra, and faces with three equivalent SrP7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 20–54°. There are a spread of Sr–P bond distances ranging from 3.22–3.34 Å. In the second Sr2+ site, Sr2+ is bonded to six P3- atoms to form SrP6 octahedra that share corners with five SrP6 octahedra, corners with six equivalent SrP7 pentagonal bipyramids, corners with four equivalent SnP4 tetrahedra, edges with two equivalent SrP6 octahedra, an edgeedge with one SrP7 pentagonal bipyramid, edges with two equivalent SnP4 tetrahedra, a faceface with one SrP6 octahedra, and faces with two equivalent SrP7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 29–57°. There are a spread of Sr–P bond distances ranging from 3.05–3.19 Å. In the third Sr2+ site, Sr2+ is bonded to six P3- atoms to form SrP6 octahedra that share corners with six equivalent SrP6 octahedra, corners with six equivalent SrP7 pentagonal bipyramids, edges with two equivalent SrP6 octahedra, edges with two equivalent SrP7 pentagonal bipyramids, edges with four equivalent SnP4 tetrahedra, and faces with two equivalent SrP6 octahedra. The corner-sharing octahedra tilt angles range from 42–57°. There are four shorter (3.14 Å) and two longer (3.16 Å) Sr–P bond lengths. Sn4+ is bonded to four P3- atoms to form SnP4 tetrahedra that share corners with four equivalent SrP6 octahedra, corners with four equivalent SrP7 pentagonal bipyramids, corners with two equivalent SnP4 tetrahedra, edges with four SrP6 octahedra, and edges with two equivalent SrP7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 41–62°. There are a spread of Sn–P bond distances ranging from 2.53–2.62 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 6-coordinate geometry to four Sr2+ and two equivalent Sn4+ atoms. In the second P3- site, P3- is bonded to six Sr2+ and one Sn4+ atom to form a mixture of distorted edge, face, and corner-sharing PSr6Sn pentagonal bipyramids. In the third P3- site, P3- is bonded to six Sr2+ and one Sn4+ atom to form a mixture of distorted edge, face, and corner-sharing PSr6Sn pentagonal bipyramids.