Materials Data on Ca4Si6Pb6Cl2O21 by Materials Project

Abstract

Ca4Pb6Si6O21Cl2 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 pentagonal pyramids that share corners with six equivalent SiO4 tetrahedra and a faceface with one CaO6 pentagonal pyramid. There are three shorter (2.37 Å) and three longer (2.45 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to six equivalent O2- atoms to form distorted CaO6 pentagonal pyramids that share corners with six equivalent SiO4 tetrahedra and faces with two equivalent CaO6 pentagonal pyramids. All Ca–O bond lengths are 2.37 Å. In the third Ca2+ site, Ca2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are six shorter (2.46 Å) and three longer (2.80 Å) Ca–O bond lengths. Pb2+ is bonded in a 3-coordinate geometry to three O2- and two Cl1- atoms. There are two shorter (2.36 Å) and one longer (2.40 Å) Pb–O bond lengths. There are one shorter (3.05 Å) and one longer (3.30 Å) Pb–Cl bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three CaO6 pentagonal pyramids and a cornercorner with one SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Pb2+, one Si4+, and one Cl1- atom. The O–Cl bond length is 3.18 Å. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two Ca2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded to two Ca2+, one Pb2+, and one Si4+ atom to form a mixture of distorted edge and corner-sharing OCa2SiPb tetrahedra. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 6-coordinate geometry to six equivalent Pb2+ and two equivalent Cl1- atoms. Both Cl–Cl bond lengths are 3.36 Å. In the second Cl1- site, Cl1- is bonded in a 12-coordinate geometry to six equivalent Pb2+, six equivalent O2-, and two equivalent Cl1- atoms.