Materials Data on Ca3SiBr2 by Materials Project

Abstract

Ca3SiBr2 is Caswellsilverite-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six Br1- atoms to form CaBr6 octahedra that share corners with nine CaSi3Br3 octahedra, edges with nine CaBr6 octahedra, and a faceface with one CaSi3Br3 octahedra. The corner-sharing octahedra tilt angles range from 11–46°. All Ca–Br bond lengths are 2.99 Å. In the second Ca2+ site, Ca2+ is bonded to three equivalent Si4- and three equivalent Br1- atoms to form distorted CaSi3Br3 octahedra that share corners with twelve CaBr6 octahedra, edges with six equivalent CaSi3Br3 octahedra, and faces with two CaBr6 octahedra. The corner-sharing octahedra tilt angles range from 46–49°. All Ca–Si bond lengths are 2.96 Å. All Ca–Br bond lengths are 3.64 Å. In the third Ca2+ site, Ca2+ is bonded to three equivalent Si4- and three equivalent Br1- atoms to form CaSi3Br3 octahedra that share corners with nine CaBr6 octahedra, edges with nine CaBr6 octahedra, and a faceface with one CaSi3Br3 octahedra. The corner-sharing octahedra tilt angles range from 11–49°. All Ca–Si bond lengths are 2.96 Å. All Ca–Br bond lengths are 3.52 Å. Si4- is bonded in a 6-coordinate geometry to six Ca2+ atoms. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded to six Ca2+ atoms to form distorted edge-sharing BrCa6 octahedra. In the second Br1- site, Br1- is bonded in a 3-coordinate geometry to six Ca2+ atoms.