DOI: 10.17188/1686997
title: Materials Data on Na4CaZr2TiSi4(O8F)2 by Materials Project

description: Na4CaZr2TiSi4(O8F)2 is Esseneite-derived structured and crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- and two equivalent F1- atoms to form distorted NaO4F2 octahedra that share corners with two equivalent ZrO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with two equivalent NaO6F2 hexagonal bipyramids, edges with two equivalent CaO4F2 octahedra, and edges with two equivalent TiO6 octahedra. The corner-sharing octahedral tilt angles are 68°. There are two shorter (2.41 Å) and two longer (2.63 Å) Na–O bond lengths. Both Na–F bond lengths are 2.33 Å. In the second Na1+ site, Na1+ is bonded in a 8-coordinate geometry to seven O2- and one F1- atom. There are a spread of Na–O bond distances ranging from 2.36–2.97 Å. The Na–F bond length is 2.22 Å. In the third Na1+ site, Na1+ is bonded to six O2- and two equivalent F1- atoms to form distorted NaO6F2 hexagonal bipyramids that share edges with two equivalent NaO4F2 octahedra, edges with two equivalent CaO4F2 octahedra, edges with two equivalent TiO6 octahedra, and edges with four SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.54–2.73 Å. Both Na–F bond lengths are 2.22 Å. Ca2+ is bonded to four O2- and two equivalent F1- atoms to form distorted CaO4F2 octahedra that share corners with two equivalent ZrO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with two equivalent NaO6F2 hexagonal bipyramids, edges with two equivalent NaO4F2 octahedra, and edges with two equivalent TiO6 octahedra. The corner-sharing octahedral tilt angles are 66°. There are two shorter (2.32 Å) and two longer (2.43 Å) Ca–O bond lengths. Both Ca–F bond lengths are 2.24 Å. Zr4+ is bonded to six O2- atoms to form ZrO6 octahedra that share a cornercorner with one NaO4F2 octahedra, a cornercorner with one CaO4F2 octahedra, a cornercorner with one TiO6 octahedra, corners with five SiO4 tetrahedra, and an edgeedge with one ZrO6 octahedra. The corner-sharing octahedra tilt angles range from 44–68°. There are a spread of Zr–O bond distances ranging from 2.03–2.31 Å. Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent ZrO6 octahedra, corners with four SiO4 tetrahedra, edges with two equivalent NaO6F2 hexagonal bipyramids, edges with two equivalent NaO4F2 octahedra, and edges with two equivalent CaO4F2 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Ti–O bond distances ranging from 1.94–2.03 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 CaO4F2 octahedra, a cornercorner with one TiO6 octahedra, corners with two equivalent ZrO6 octahedra, a cornercorner with one SiO4 tetrahedra, and an edgeedge with one NaO6F2 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 37–68°. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO4F2 octahedra, a cornercorner with one TiO6 octahedra, corners with three equivalent ZrO6 octahedra, a cornercorner with one SiO4 tetrahedra, and an edgeedge with one NaO6F2 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 35–75°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to three Na1+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Zr4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Zr4+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Zr4+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Ca2+, one Ti4+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Zr4+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Na1+, one Ca2+, one Zr4+, and one Ti4+ atom. F1- is bonded to three Na1+ and one Ca2+ atom to form a mixture of distorted corner and edge-sharing FNa3Ca tetrahedra.