DOE OSTI2020
Ho10Ti6O27 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.23–2.34 Å. In the second Ho3+ site, Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.13–2.36 Å. In the third Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.22–2.65 Å. In the fourth Ho3+ site, Ho3+ is bonded to seven O2- atoms to form distorted HoO7 pentagonal bipyramids that share a cornercorner with one HoO7 hexagonal pyramid, corners with two equivalent TiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedral tilt angles are 54°. There are a spread of Ho–O bond distances ranging from 2.20–2.57 Å. In the fifth Ho3+ site, Ho3+ is bonded to seven O2- atoms to form distorted HoO7 hexagonal pyramids that share corners with two equivalent TiO6 octahedra, a cornercorner with one HoO7 pentagonal bipyramid, and edges with four TiO6 octahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Ho–O bond distances ranging from 2.20–2.45 Å. In the sixth Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.21–2.64 Å. In the seventh Ho3+ site, Ho3+ is bonded to seven O2- atoms to form distorted HoO7 pentagonal bipyramids that share corners with three TiO6 octahedra and edges with two equivalent TiO6 octahedra. The corner-sharing octahedra tilt angles range from 50–71°. There are a spread of Ho–O bond distances ranging from 2.17–2.40 Å. In the eighth Ho3+ site, Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.12–2.41 Å. There are four inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with three TiO6 octahedra, a cornercorner with one HoO7 pentagonal bipyramid, and an edgeedge with one HoO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 30–49°. There are a spread of Ti–O bond distances ranging from 1.88–2.43 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share a cornercorner with one HoO7 hexagonal pyramid, corners with five TiO6 octahedra, a cornercorner with one HoO7 pentagonal bipyramid, an edgeedge with one HoO7 hexagonal pyramid, and an edgeedge with one HoO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 28–61°. There are a spread of Ti–O bond distances ranging from 1.85–2.24 Å. In the third Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted TiO6 octahedra that share corners with five TiO6 octahedra and edges with two equivalent HoO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 30–61°. There are a spread of Ti–O bond distances ranging from 1.85–2.29 Å. In the fourth Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five TiO6 octahedra, a cornercorner with one HoO7 pentagonal bipyramid, and edges with two equivalent HoO7 hexagonal pyramids. The corner-sharing octahedra tilt angles range from 47–52°. There are a spread of Ti–O bond distances ranging from 1.92–2.15 Å. There are nineteen inequivalent O2- sites. In the first O2- site, O2- is bonded to three Ho3+ and one Ti4+ atom to form distorted OHo3Ti tetrahedra that share corners with nine OHo3Ti tetrahedra and an edgeedge with one OHo4 tetrahedra. In the second O2- site, O2- is bonded to two Ho3+ and two equivalent Ti4+ atoms to form distorted corner-sharing OHo2Ti2 tetrahedra. In the third O2- site, O2- is bonded to three Ho3+ and one Ti4+ atom to form distorted OHo3Ti tetrahedra that share corners with nine OHo3Ti tetrahedra and an edgeedge with one OHo4 tetrahedra. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Ho3+ and two Ti4+ atoms. In the fifth O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+ and two equivalent Ti4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ho3+ and two Ti4+ atoms. In the eighth O2- site, O2- is bonded to three Ho3+ and one Ti4+ atom to form corner-sharing OHo3Ti tetrahedra. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Ho3+ and one Ti4+ atom. In the tenth O2- site, O2- is bonded to four Ho3+ atoms to form OHo4 tetrahedra that share corners with ten OHo3Ti tetrahedra and an edgeedge with one OHo4 tetrahedra. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to two Ho3+ and two Ti4+ atoms. In the twelfth O2- site, O2- is bonded to four Ho3+ atoms to form distorted OHo4 tetrahedra that share corners with eight OHo4 tetrahedra and an edgeedge with one OHo3Ti tetrahedra. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Ho3+ and one Ti4+ atom. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ho3+ and two Ti4+ atoms. In the fifteenth O2- site, O2- is bonded in a trigonal planar geometry to one Ho3+ and two equivalent Ti4+ atoms. In the sixteenth O2- site, O2- is bonded to three Ho3+ and one Ti4+ atom to form OHo3Ti tetrahedra that share corners with five OHo3Ti tetrahedra and edges with three OHo4 tetrahedra. In the seventeenth O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the eighteenth O2- site, O2- is bonded to two Ho3+ and two Ti4+ atoms to form a mixture of distorted corner and edge-sharing OHo2Ti2 tetrahedra. In the nineteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+ and two equivalent Ti4+ atoms.