Materials Data on Na4Si2PbSe6 by Materials Project

Na4PbSi2Se6 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent PbSe6 octahedra, corners with two equivalent SiSiSe3 tetrahedra, edges with two equivalent PbSe6 octahedra, edges with eight NaSe6 octahedra, and edges with two equivalent SiSiSe3 tetrahedra. The corner-sharing octahedral tilt angles are 7°. There are a spread of Na–Se bond distances ranging from 3.00–3.23 Å. In the second Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent PbSe6 octahedra, corners with two equivalent SiSiSe3 tetrahedra, edges with two equivalent PbSe6 octahedra, edges with eight NaSe6 octahedra, and edges with two equivalent SiSiSe3 tetrahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Na–Se bond distances ranging from 3.01–3.15 Å. In the third Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent PbSe6 octahedra, corners with two equivalent SiSiSe3 tetrahedra, edges with two equivalent PbSe6 octahedra, edges with eight NaSe6 octahedra, and edges with two equivalent SiSiSe3 tetrahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Na–Se bond distances ranging from 3.01–3.15 Å. In the fourth Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with six NaSe6 octahedra, corners with six equivalent SiSiSe3 tetrahedra, edges with three equivalent PbSe6 octahedra, and edges with six NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are two shorter (3.10 Å) and four longer (3.12 Å) Na–Se bond lengths. Pb2+ is bonded to six Se1- atoms to form PbSe6 octahedra that share corners with six NaSe6 octahedra, corners with six equivalent SiSiSe3 tetrahedra, and edges with nine NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Pb–Se bond distances ranging from 3.10–3.13 Å. Si is bonded to one Si and three Se1- atoms to form distorted SiSiSe3 tetrahedra that share corners with three equivalent PbSe6 octahedra, corners with three SeNa4SiPb octahedra, corners with six NaSe6 octahedra, and edges with three NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 19–77°. The Si–Si bond length is 2.35 Å. There are one shorter (2.30 Å) and two longer (2.31 Å) Si–Se bond lengths. There are three inequivalent Se1- sites. In the first Se1- site, Se1- is bonded to four Na1+, one Pb2+, and one Si atom to form distorted SeNa4SiPb octahedra that share corners with seven SeNa4SiPb octahedra, a cornercorner with one SiSiSe3 tetrahedra, and edges with ten SeNa4SiPb octahedra. The corner-sharing octahedra tilt angles range from 0–91°. In the second Se1- site, Se1- is bonded to four Na1+, one Pb2+, and one Si atom to form distorted SeNa4SiPb octahedra that share corners with seven SeNa4SiPb octahedra, a cornercorner with one SiSiSe3 tetrahedra, and edges with ten SeNa4SiPb octahedra. The corner-sharing octahedra tilt angles range from 0–91°. In the third Se1- site, Se1- is bonded to four Na1+, one Pb2+, and one Si atom to form distorted SeNa4SiPb octahedra that share corners with seven SeNa4SiPb octahedra, a cornercorner with one SiSiSe3 tetrahedra, and edges with ten SeNa4SiPb octahedra. The corner-sharing octahedra tilt angles range from 0–92°.