Materials Data on Ca2SiSe4 by Materials Project
Ca2SiSe4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six Se2- atoms to form CaSe6 octahedra that share corners with four equivalent CaSe6 octahedra, corners with two equivalent SiSe4 tetrahedra, edges with four CaSe6 octahedra, and edges with two equivalent SiSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Ca–Se bond distances ranging from 2.92–3.02 Å. In the second Ca2+ site, Ca2+ is bonded to six Se2- atoms to form CaSe6 octahedra that share corners with eight CaSe6 octahedra, corners with four equivalent SiSe4 tetrahedra, edges with two equivalent CaSe6 octahedra, and an edgeedge with one SiSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 50–63°. There are a spread of Ca–Se bond distances ranging from 2.95–3.04 Å. Si4+ is bonded to four Se2- atoms to form SiSe4 tetrahedra that share corners with six CaSe6 octahedra and edges with three CaSe6 octahedra. The corner-sharing octahedra tilt angles range from 54–57°. There are one shorter (2.28 Å) and three longer (2.31 Å) Si–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Ca2+ and one Si4+ atom to form distorted corner-sharing SeCa3Si trigonal pyramids. In the second Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to three Ca2+ and one Si4+ atom. In the third Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to three Ca2+ and one Si4+ atom.