Materials Data on Na6Ti2O7 by Materials Project

Abstract

Na6Ti2O7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.35–2.94 Å. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.40–2.95 Å. In the third Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with two equivalent TiO4 tetrahedra, edges with two equivalent TiO4 tetrahedra, and edges with two equivalent NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.40–2.64 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with four equivalent TiO4 tetrahedra and edges with two equivalent NaO6 octahedra. All Na–O bond lengths are 2.35 Å. Ti4+ is bonded to four O2- atoms to form TiO4 tetrahedra that share a cornercorner with one NaO6 octahedra, a cornercorner with one TiO4 tetrahedra, corners with two equivalent NaO4 trigonal pyramids, and an edgeedge with one NaO6 octahedra. The corner-sharing octahedral tilt angles are 21°. There is three shorter (1.82 Å) and one longer (1.91 Å) Ti–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to five Na1+ and one Ti4+ atom. In the second O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Ti4+ atom. In the third O2- site, O2- is bonded to five Na1+ and one Ti4+ atom to form a mixture of distorted corner and edge-sharing ONa5Ti octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to four Na1+ and two equivalent Ti4+ atoms.