Materials Data on Ca3SiBr2 by Materials Project

Abstract

Ca3SiBr2 crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of one Ca3SiBr2 sheet oriented in the (0, 0, 1) direction. 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 three equivalent CaSi3Br tetrahedra and edges with six equivalent CaBr6 octahedra. There are a spread of Ca–Br bond distances ranging from 2.98–3.04 Å. In the second Ca2+ site, Ca2+ is bonded to three equivalent Si4- and one Br1- atom to form CaSi3Br tetrahedra that share corners with three equivalent CaBr6 octahedra and corners with six equivalent CaSi3Br tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are two shorter (2.91 Å) and one longer (2.92 Å) Ca–Si bond lengths. The Ca–Br bond length is 3.46 Å. In the third Ca2+ site, Ca2+ is bonded in a trigonal non-coplanar geometry to three equivalent Si4- atoms. There are two shorter (2.91 Å) and one longer (2.92 Å) Ca–Si bond lengths. Si4- is bonded to six Ca2+ atoms to form distorted SiCa6 octahedra that share corners with three equivalent BrCa4 tetrahedra and edges with six equivalent SiCa6 octahedra. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted T-shaped geometry to three equivalent Ca2+ atoms. In the second Br1- site, Br1- is bonded to four Ca2+ atoms to form distorted BrCa4 tetrahedra that share corners with three equivalent SiCa6 octahedra and corners with six equivalent BrCa4 tetrahedra. The corner-sharing octahedra tilt angles range from 62–67°.