DOE OSTI2020
Cd2Te2O7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are five inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Cd–O bond distances ranging from 2.25–2.62 Å. In the second Cd2+ site, Cd2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.25–2.47 Å. In the third Cd2+ site, Cd2+ is bonded to eight O2- atoms to form distorted CdO8 hexagonal bipyramids that share an edgeedge with one CdO8 hexagonal bipyramid, an edgeedge with one CdO6 octahedra, and edges with three TeO6 octahedra. There are a spread of Cd–O bond distances ranging from 2.37–2.63 Å. In the fourth Cd2+ site, Cd2+ is bonded to six O2- atoms to form CdO6 octahedra that share corners with four TeO6 octahedra and edges with two equivalent CdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 54–55°. There are a spread of Cd–O bond distances ranging from 2.27–2.31 Å. In the fifth Cd2+ site, Cd2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cd–O bond distances ranging from 2.18–2.46 Å. There are four inequivalent Te5+ sites. In the first Te5+ site, Te5+ is bonded in a 3-coordinate geometry to three O2- atoms. There is one shorter (1.92 Å) and two longer (1.94 Å) Te–O bond length. In the second Te5+ site, Te5+ is bonded to six O2- atoms to form TeO6 octahedra that share a cornercorner with one CdO6 octahedra, corners with two equivalent TeO6 octahedra, and an edgeedge with one CdO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 30–55°. There are a spread of Te–O bond distances ranging from 1.91–2.08 Å. In the third Te5+ site, Te5+ is bonded in a 3-coordinate geometry to four O2- atoms. There are a spread of Te–O bond distances ranging from 1.88–2.64 Å. In the fourth Te5+ site, Te5+ is bonded to six O2- atoms to form TeO6 octahedra that share a cornercorner with one CdO6 octahedra, corners with two equivalent TeO6 octahedra, and edges with two equivalent CdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 30–54°. There are a spread of Te–O bond distances ranging from 1.90–2.10 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Te5+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Te5+ atom. In the third O2- site, O2- is bonded to three Cd2+ and one Te5+ atom to form a mixture of distorted corner and edge-sharing OCd3Te tetrahedra. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Te5+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cd2+ and one Te5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Te5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cd2+ and two Te5+ atoms. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two Cd2+ and two Te5+ atoms. In the ninth O2- site, O2- is bonded to three Cd2+ and one Te5+ atom to form a mixture of distorted corner and edge-sharing OCd3Te tetrahedra. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Cd2+ and one Te5+ atom. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to three Cd2+ and one Te5+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Cd2+ and one Te5+ atom. In the thirteenth O2- site, O2- is bonded to three Cd2+ and one Te5+ atom to form a mixture of distorted corner and edge-sharing OCd3Te tetrahedra. In the fourteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Te5+ atoms.