DOI: 10.17188/1190990
title: Materials Data on Ca3ZrSi2O9 by Materials Project

description: Ca3ZrSi2O9 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–3.03 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with two equivalent ZrO6 octahedra, corners with five SiO4 tetrahedra, and an edgeedge with one ZrO6 octahedra. The corner-sharing octahedra tilt angles range from 53–62°. There are a spread of Ca–O bond distances ranging from 2.34–2.53 Å. In the third Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.76 Å. Zr4+ is bonded to six O2- atoms to form ZrO6 octahedra that share corners with two equivalent CaO6 octahedra, corners with three SiO4 tetrahedra, an edgeedge with one CaO6 octahedra, and an edgeedge with one ZrO6 octahedra. The corner-sharing octahedra tilt angles range from 53–62°. There are a spread of Zr–O bond distances ranging from 2.02–2.24 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one ZrO6 octahedra, corners with two equivalent CaO6 octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–48°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent ZrO6 octahedra, corners with three equivalent CaO6 octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–77°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+, one Zr4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ca2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded to three Ca2+ and one Si4+ atom to form distorted corner-sharing OCa3Si tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Zr4+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Ca2+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Zr4+, and one Si4+ atom. In the eighth O2- site, O2- is bonded to three Ca2+ and one Zr4+ atom to form distorted OCa3Zr tetrahedra that share corners with five OCa3Si tetrahedra and edges with two OCa3Zr tetrahedra. In the ninth O2- site, O2- is bonded to two Ca2+ and two equivalent Zr4+ atoms to form distorted OCa2Zr2 tetrahedra that share corners with four OCa3Si tetrahedra and edges with two OCa3Zr tetrahedra.