Materials Data on Na2Sn2Se5 by Materials Project

Abstract

Na2Sn2Se5 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to seven Se2- atoms to form distorted NaSe7 pentagonal bipyramids that share corners with four equivalent NaSe7 pentagonal bipyramids, corners with three equivalent SnSe4 tetrahedra, edges with two equivalent NaSe6 octahedra, an edgeedge with one SnSe4 tetrahedra, and faces with two equivalent NaSe6 octahedra. There are a spread of Na–Se bond distances ranging from 3.10–3.45 Å. In the second Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with four equivalent NaSe6 octahedra, corners with four equivalent SnSe4 tetrahedra, edges with two equivalent NaSe7 pentagonal bipyramids, and faces with two equivalent NaSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 15–27°. There are a spread of Na–Se bond distances ranging from 3.05–3.29 Å. There are two inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share corners with four equivalent NaSe6 octahedra, corners with three equivalent NaSe7 pentagonal bipyramids, and an edgeedge with one NaSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 38–89°. There are a spread of Sn–Se bond distances ranging from 2.49–2.60 Å. In the second Sn4+ site, Sn4+ is bonded in a distorted rectangular see-saw-like geometry to four Se2- atoms. There are a spread of Sn–Se bond distances ranging from 2.50–2.61 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to two Na1+ and two Sn4+ atoms. In the second Se2- site, Se2- is bonded to four Na1+ and one Sn4+ atom to form distorted SeNa4Sn trigonal bipyramids that share corners with four equivalent SeNa4Sn trigonal bipyramids, corners with three equivalent SeNa2Sn2 trigonal pyramids, and an edgeedge with one SeNa2Sn2 trigonal pyramid. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to four Na1+ and one Sn4+ atom. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to one Na1+ and two Sn4+ atoms. In the fifth Se2- site, Se2- is bonded to two Na1+ and two Sn4+ atoms to form a mixture of distorted edge and corner-sharing SeNa2Sn2 trigonal pyramids.