Materials Data on Na2Ti2F7 by Materials Project
Na2Ti2F7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are six inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted body-centered cubic geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.43–2.90 Å. In the second Na1+ site, Na1+ is bonded to eight F1- atoms to form distorted NaF8 hexagonal bipyramids that share corners with two equivalent TiF6 octahedra and edges with six TiF6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Na–F bond distances ranging from 2.28–2.77 Å. In the third Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.42–2.93 Å. In the fourth Na1+ site, Na1+ is bonded in a distorted body-centered cubic geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.39–2.85 Å. In the fifth Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.32–2.97 Å. In the sixth Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.20–3.01 Å. There are five inequivalent Ti+2.50+ sites. In the first Ti+2.50+ site, Ti+2.50+ is bonded to six F1- atoms to form TiF6 octahedra that share corners with four TiF6 octahedra and edges with two equivalent NaF8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 38–43°. There are a spread of Ti–F bond distances ranging from 2.03–2.05 Å. In the second Ti+2.50+ site, Ti+2.50+ is bonded to six F1- atoms to form corner-sharing TiF6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Ti–F bond distances ranging from 2.02–2.08 Å. In the third Ti+2.50+ site, Ti+2.50+ is bonded to six F1- atoms to form TiF6 octahedra that share a cornercorner with one NaF8 hexagonal bipyramid and corners with four TiF6 octahedra. The corner-sharing octahedra tilt angles range from 45–50°. There are a spread of Ti–F bond distances ranging from 2.03–2.07 Å. In the fourth Ti+2.50+ site, Ti+2.50+ is bonded to six F1- atoms to form TiF6 octahedra that share corners with six TiF6 octahedra and an edgeedge with one NaF8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 31–56°. There are a spread of Ti–F bond distances ranging from 2.02–2.07 Å. In the fifth Ti+2.50+ site, Ti+2.50+ is bonded to six F1- atoms to form TiF6 octahedra that share corners with six TiF6 octahedra and an edgeedge with one NaF8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 31–56°. There are a spread of Ti–F bond distances ranging from 2.03–2.05 Å. There are fourteen inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the second F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the third F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the fourth F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the fifth F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the sixth F1- site, F1- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two Ti+2.50+ atoms. In the seventh F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the eighth F1- site, F1- is bonded in a 4-coordinate geometry to two Na1+ and two Ti+2.50+ atoms. In the ninth F1- site, F1- is bonded in a bent 150 degrees geometry to two Na1+ and two Ti+2.50+ atoms. In the tenth F1- site, F1- is bonded in a distorted bent 120 degrees geometry to two Na1+ and two Ti+2.50+ atoms. In the eleventh F1- site, F1- is bonded to three Na1+ and one Ti+2.50+ atom to form a mixture of distorted edge and corner-sharing FNa3Ti tetrahedra. In the twelfth F1- site, F1- is bonded to three Na1+ and one Ti+2.50+ atom to form a mixture of distorted edge and corner-sharing FNa3Ti tetrahedra. In the thirteenth F1- site, F1- is bonded to three Na1+ and one Ti+2.50+ atom to form a mixture of distorted edge and corner-sharing FNa3Ti tetrahedra. In the fourteenth F1- site, F1- is bonded to three Na1+ and one Ti+2.50+ atom to form a mixture of distorted edge and corner-sharing FNa3Ti tetrahedra.