DOE OSTI2020
Na2Ti7O15 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.46 Å) and two longer (2.48 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.58–3.01 Å. In the third Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.52 Å) and two longer (2.66 Å) Na–O bond lengths. In the fourth Na1+ site, Na1+ is bonded in a 4-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.52–3.03 Å. There are fourteen inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 33°. There are a spread of Ti–O bond distances ranging from 1.75–2.30 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. There are a spread of Ti–O bond distances ranging from 1.79–2.27 Å. In the third Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–28°. There are a spread of Ti–O bond distances ranging from 1.83–2.22 Å. In the fourth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–25°. There are a spread of Ti–O bond distances ranging from 1.86–2.15 Å. In the fifth Ti4+ site, Ti4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ti–O bond distances ranging from 1.75–2.38 Å. In the sixth Ti4+ site, Ti4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ti–O bond distances ranging from 1.76–2.31 Å. In the seventh Ti4+ site, Ti4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ti–O bond distances ranging from 1.75–2.33 Å. In the eighth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 8–31°. There are a spread of Ti–O bond distances ranging from 1.80–2.25 Å. In the ninth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are a spread of Ti–O bond distances ranging from 1.78–2.27 Å. In the tenth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of Ti–O bond distances ranging from 1.84–2.19 Å. In the eleventh Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. There are a spread of Ti–O bond distances ranging from 1.79–2.26 Å. In the twelfth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 33°. There are a spread of Ti–O bond distances ranging from 1.83–2.28 Å. In the thirteenth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 7–31°. There are a spread of Ti–O bond distances ranging from 1.83–2.24 Å. In the fourteenth Ti4+ site, Ti4+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 5–27°. There are a spread of Ti–O bond distances ranging from 1.84–2.19 Å. There are thirty inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share corners with three ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and edges with four OTi4 trigonal pyramids. In the second O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share corners with three ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and edges with four OTi4 trigonal pyramids. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+ and two Ti4+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+ and two Ti4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two Ti4+ atoms. In the sixth O2- site, O2- is bonded to two equivalent Na1+ and two Ti4+ atoms to form distorted ONa2Ti2 tetrahedra that share corners with two equivalent ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and an edgeedge with one OTi4 trigonal pyramid. In the seventh O2- site, O2- is bonded in a distorted linear geometry to two Ti4+ atoms. In the eighth O2- site, O2- is bonded in a linear geometry to two equivalent Na1+ and two Ti4+ atoms. In the ninth O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share a cornercorner with one ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and edges with four OTi4 trigonal pyramids. In the tenth O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and edges with four OTi4 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a water-like geometry to two Ti4+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+ and two Ti4+ atoms. In the thirteenth O2- site, O2- is bonded in a linear geometry to two Ti4+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted linear geometry to two equivalent Na1+ and two Ti4+ atoms. In the fifteenth O2- site, O2- is bonded to four Ti4+ atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the sixteenth O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share corners with three OTi4 trigonal pyramids, an edgeedge with one ONa2Ti2 tetrahedra, and edges with two equivalent OTi4 trigonal pyramids. In the seventeenth O2- site, O2- is bonded in a water-like geometry to two Ti4+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+ and two Ti4+ atoms. In the nineteenth O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share a cornercorner with one ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and edges with two equivalent OTi4 trigonal pyramids. In the twentieth O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share a cornercorner with one ONa2Ti2 tetrahedra, corners with three OTi4 trigonal pyramids, and edges with two equivalent OTi4 trigonal pyramids. In the twenty-first O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent ONa2Ti2 tetrahedra, corners with four OTi4 trigonal pyramids, an edgeedge with one ONa2Ti2 tetrahedra, and edges with four OTi4 trigonal pyramids. In the twenty-second O2- site, O2- is bonded to four Ti4+ atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent ONa2Ti2 tetrahedra, corners with four OTi4 trigonal pyramids, an edgeedge with one ONa2Ti2 tetrahedra, and edges with four OTi4 trigonal pyramids. In the twenty-third O2- site, O2- is bonded in a linear geometry to two Ti4+ atoms. In the twenty-fourth O2- site, O2- is bonded in a linear geometry to two equivalent Na1+ and two Ti4+ atoms. In the twenty-fifth O2- site, O2- is bonded in a 3-coordinate geometry to three Ti4+ atoms. In the twenty-sixth O2- site, O2- is bonded in a distorted T-shaped geometry to three Ti4+ atoms. In the twenty-seventh O2- site, O2- is bonded in a distorted T-shaped geometry to three Ti4+ atoms. In the twenty-eighth O2- site, O2- is bonded in a distorted T-shaped geometry to three Ti4+ atoms. In the twenty-ninth O2- site, O2- is bonded to two equivalent Na1+ and two Ti4+ atoms to form ONa2Ti2 tetrahedra that share corners with four ONa2Ti2 tetrahedra, corners with six OTi4 trigonal pyramids, an edgeedge with one ONa2Ti2 tetrahedra, and an edgeedge with one OTi4 trigonal pyramid. In the thirtieth O2- site, O2- is bonded to two equivalent Na1+ and two Ti4+ atoms to form ONa2Ti2 tetrahedra that share corners with four ONa2Ti2 tetrahedra, corners with six OTi4 trigonal pyramids, an edgeedge with one ONa2Ti2 tetrahedra, and an edgeedge with one OTi4 trigonal pyramid.