DOI: 10.17188/1746933
title: Materials Data on Na2Sr(SiO3)2 by Materials Project

description: Na2SrSi2O6 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with eight equivalent NaO8 hexagonal bipyramids, edges with four equivalent SrO8 hexagonal bipyramids, edges with two equivalent NaO6 octahedra, and edges with six SiO4 tetrahedra. There are four shorter (2.78 Å) and four longer (2.79 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with eight NaO8 hexagonal bipyramids, edges with two equivalent NaO8 hexagonal bipyramids, edges with two equivalent SrO8 hexagonal bipyramids, edges with two equivalent NaO6 octahedra, and edges with six SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.75–2.80 Å. In the third Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with four equivalent SrO8 hexagonal bipyramids, corners with two equivalent SiO4 tetrahedra, edges with four equivalent NaO8 hexagonal bipyramids, edges with two equivalent SrO6 octahedra, edges with four equivalent SiO4 tetrahedra, and faces with two equivalent NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.40–2.90 Å. In the fourth Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with six SiO4 tetrahedra, edges with three NaO8 hexagonal bipyramids, a faceface with one NaO8 hexagonal bipyramid, faces with two equivalent SrO8 hexagonal bipyramids, and a faceface with one SrO6 octahedra. There are a spread of Na–O bond distances ranging from 2.32–2.70 Å. There are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to six O2- atoms to form SrO6 octahedra that share corners with six SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, edges with four equivalent SrO8 hexagonal bipyramids, and faces with two equivalent NaO6 octahedra. There are two shorter (2.45 Å) and four longer (2.47 Å) Sr–O bond lengths. In the second Sr2+ site, Sr2+ is bonded to eight O2- atoms to form SrO8 hexagonal bipyramids that share corners with two equivalent NaO8 hexagonal bipyramids, corners with two equivalent SrO8 hexagonal bipyramids, corners with two equivalent SiO4 tetrahedra, edges with four NaO8 hexagonal bipyramids, edges with two equivalent SrO6 octahedra, edges with four SiO4 tetrahedra, and faces with two equivalent NaO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.45–2.82 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 SrO8 hexagonal bipyramid, a cornercorner with one SrO6 octahedra, corners with two equivalent NaO6 octahedra, corners with two SiO4 tetrahedra, an edgeedge with one SrO8 hexagonal bipyramid, and edges with four NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 41–48°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, a cornercorner with one SrO6 octahedra, corners with two equivalent NaO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with two equivalent SrO8 hexagonal bipyramids, and edges with three NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 36–51°. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to three Na1+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+, one Sr2+, and two Si4+ atoms. In the third O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+, one Sr2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two Na1+, two Sr2+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, three Sr2+, and one Si4+ atom.