Materials Data on Cu5Sn2Se7 by Materials Project
Cu5Sn2Se7 is Enargite-like structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are three inequivalent Cu+1.20+ sites. In the first Cu+1.20+ site, Cu+1.20+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with four equivalent SnSe4 tetrahedra and corners with eight CuSe4 tetrahedra. All Cu–Se bond lengths are 2.42 Å. In the second Cu+1.20+ site, Cu+1.20+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with five equivalent SnSe4 tetrahedra and corners with seven CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.40–2.43 Å. In the third Cu+1.20+ site, Cu+1.20+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with four equivalent SnSe4 tetrahedra and corners with eight CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.41–2.43 Å. Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share a cornercorner with one SnSe4 tetrahedra and corners with eleven CuSe4 tetrahedra. There are three shorter (2.61 Å) and one longer (2.68 Å) Sn–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Cu+1.20+ and one Sn4+ atom to form corner-sharing SeCu3Sn tetrahedra. In the second Se2- site, Se2- is bonded to two equivalent Cu+1.20+ and two equivalent Sn4+ atoms to form corner-sharing SeCu2Sn2 tetrahedra. In the third Se2- site, Se2- is bonded to three Cu+1.20+ and one Sn4+ atom to form corner-sharing SeCu3Sn tetrahedra. In the fourth Se2- site, Se2- is bonded to three Cu+1.20+ and one Sn4+ atom to form corner-sharing SeCu3Sn tetrahedra.