DOI: 10.17188/1746293
title: Materials Data on Na2CaZrSi2O7F2 by Materials Project

description: Na2CaZrSi2O7F2 is Esseneite-derived structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to three O2- and three F1- atoms to form distorted NaO3F3 octahedra that share a cornercorner with one ZrO5F octahedra, corners with three SiO4 tetrahedra, an edgeedge with one ZrO5F octahedra, and edges with four NaO3F3 octahedra. The corner-sharing octahedral tilt angles are 63°. There are a spread of Na–O bond distances ranging from 2.53–2.65 Å. There are a spread of Na–F bond distances ranging from 2.24–2.40 Å. In the second Na1+ site, Na1+ is bonded to three O2- and three F1- atoms to form distorted NaO3F3 octahedra that share corners with two equivalent ZrO5F octahedra, corners with three SiO4 tetrahedra, an edgeedge with one ZrO5F octahedra, and edges with four NaO3F3 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Na–O bond distances ranging from 2.38–2.63 Å. There are a spread of Na–F bond distances ranging from 2.32–2.41 Å. Ca2+ is bonded in a 8-coordinate geometry to seven O2- and one F1- atom. There are a spread of Ca–O bond distances ranging from 2.27–2.83 Å. The Ca–F bond length is 2.18 Å. Zr4+ is bonded to five O2- and one F1- atom to form ZrO5F octahedra that share corners with three NaO3F3 octahedra, corners with five SiO4 tetrahedra, and edges with two NaO3F3 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Zr–O bond distances ranging from 2.09–2.11 Å. The Zr–F bond length is 2.13 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 corners with two equivalent ZrO5F octahedra, corners with three NaO3F3 octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–78°. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three NaO3F3 octahedra, corners with three equivalent ZrO5F octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 29–80°. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Ca2+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+, one Zr4+, and one Si4+ atom. In the third O2- site, O2- is bonded to two Na1+, one Ca2+, and one Si4+ atom to form distorted ONa2CaSi trigonal pyramids that share corners with two equivalent FNa3Ca tetrahedra, corners with three equivalent FNa3Zr trigonal pyramids, and an edgeedge with one FNa3Ca tetrahedra. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Zr4+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, one Zr4+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+, one Zr4+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Ca2+, one Zr4+, and one Si4+ atom. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded to three Na1+ and one Ca2+ atom to form distorted FNa3Ca tetrahedra that share corners with two equivalent ONa2CaSi trigonal pyramids, corners with two equivalent FNa3Zr trigonal pyramids, an edgeedge with one FNa3Ca tetrahedra, an edgeedge with one ONa2CaSi trigonal pyramid, and an edgeedge with one FNa3Zr trigonal pyramid. In the second F1- site, F1- is bonded to three Na1+ and one Zr4+ atom to form distorted FNa3Zr trigonal pyramids that share corners with two equivalent FNa3Ca tetrahedra, corners with three equivalent ONa2CaSi trigonal pyramids, an edgeedge with one FNa3Ca tetrahedra, and an edgeedge with one FNa3Zr trigonal pyramid.