DOE OSTI2020
Tm2Ti2O7 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are four inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.22–2.71 Å. In the second Tm3+ site, Tm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Tm–O bond distances ranging from 2.19–2.40 Å. In the third Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.20–2.44 Å. In the fourth Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.31–2.58 Å. There are four inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 34–47°. There are a spread of Ti–O bond distances ranging from 1.88–2.18 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 29–47°. There are a spread of Ti–O bond distances ranging from 1.83–2.30 Å. In the third Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 34–52°. There are a spread of Ti–O bond distances ranging from 1.78–2.25 Å. In the fourth Ti4+ site, Ti4+ is bonded to six O2- atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 29–52°. There are a spread of Ti–O bond distances ranging from 1.83–2.36 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Tm3+ and two Ti4+ atoms. In the second O2- site, O2- is bonded to three Tm3+ and one Ti4+ atom to form distorted OTm3Ti tetrahedra that share corners with two equivalent OTm3Ti tetrahedra and an edgeedge with one OTm2Ti2 trigonal pyramid. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Tm3+ and two Ti4+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Tm3+ and two Ti4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Tm3+ and one Ti4+ atom. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to three Tm3+ and two equivalent Ti4+ atoms. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two Tm3+ and two Ti4+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Tm3+ and one Ti4+ atom. In the ninth O2- site, O2- is bonded to two Tm3+ and two Ti4+ atoms to form a mixture of distorted edge and corner-sharing OTm2Ti2 tetrahedra. In the tenth O2- site, O2- is bonded to two Tm3+ and two Ti4+ atoms to form distorted OTm2Ti2 trigonal pyramids that share a cornercorner with one OTm2Ti2 tetrahedra and edges with two OTm3Ti tetrahedra. In the eleventh O2- site, O2- is bonded to two Tm3+ and two Ti4+ atoms to form a mixture of distorted edge and corner-sharing OTm2Ti2 tetrahedra. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to three Tm3+ and one Ti4+ atom. In the thirteenth O2- site, O2- is bonded in a 5-coordinate geometry to three Tm3+ and two equivalent Ti4+ atoms. In the fourteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Tm3+ and two Ti4+ atoms.