DOE OSTI2020
Gd2Ti2O7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are twelve inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Gd–O bond distances ranging from 2.32–2.69 Å. In the second Gd3+ site, Gd3+ is bonded to seven O2- atoms to form GdO7 pentagonal bipyramids that share corners with four TiO6 octahedra, edges with two equivalent TiO6 octahedra, and edges with two equivalent TiO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 51–71°. There are a spread of Gd–O bond distances ranging from 2.22–2.44 Å. In the third Gd3+ site, Gd3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Gd–O bond distances ranging from 2.32–2.69 Å. In the fourth Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Gd–O bond distances ranging from 2.26–2.45 Å. In the fifth Gd3+ site, Gd3+ is bonded to seven O2- atoms to form GdO7 pentagonal bipyramids that share corners with four TiO6 octahedra, edges with two equivalent TiO6 octahedra, and edges with two equivalent TiO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 51–71°. There are a spread of Gd–O bond distances ranging from 2.22–2.44 Å. In the sixth Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with six GdO8 hexagonal bipyramids and edges with six TiO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.59 Å. In the seventh Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with three GdO8 hexagonal bipyramids, edges with six TiO6 octahedra, and an edgeedge with one TiO7 pentagonal bipyramid. There are a spread of Gd–O bond distances ranging from 2.17–2.59 Å. In the eighth Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with six GdO8 hexagonal bipyramids and edges with six TiO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.77 Å. In the ninth Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with four GdO8 hexagonal bipyramids and edges with six TiO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.59 Å. In the tenth Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with five GdO8 hexagonal bipyramids and edges with six TiO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.55 Å. In the eleventh Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Gd–O bond distances ranging from 2.22–2.83 Å. In the twelfth Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent GdO8 hexagonal bipyramids, edges with six TiO6 octahedra, and an edgeedge with one TiO7 pentagonal bipyramid. There are a spread of Gd–O bond distances ranging from 2.17–2.59 Å. There are twelve inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to seven O2- atoms to form distorted TiO7 pentagonal bipyramids that share corners with two equivalent TiO6 octahedra, an edgeedge with one GdO8 hexagonal bipyramid, edges with two equivalent TiO6 octahedra, and edges with two equivalent GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 35°. There are a spread of Ti–O bond distances ranging from 2.04–2.16 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with four TiO6 octahedra, corners with two TiO7 pentagonal bipyramids, and edges with two GdO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 42–46°. There are a spread of Ti–O bond distances ranging from 1.94–2.03 Å. In the third Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with four equivalent TiO6 octahedra and corners with two GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. There are a spread of Ti–O bond distances ranging from 1.96–2.00 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 GdO7 pentagonal bipyramid, edges with four GdO8 hexagonal bipyramids, and an edgeedge with one TiO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 39–52°. There are a spread of Ti–O bond distances ranging from 1.92–2.03 Å. In the fifth Ti4+ site, Ti4+ is bonded to seven O2- atoms to form distorted TiO7 pentagonal bipyramids that share corners with two equivalent TiO6 octahedra, an edgeedge with one GdO8 hexagonal bipyramid, edges with two equivalent TiO6 octahedra, and edges with two equivalent GdO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 37°. There are a spread of Ti–O bond distances ranging from 1.98–2.24 Å. In the sixth Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five TiO6 octahedra, a cornercorner with one GdO7 pentagonal bipyramid, and edges with four GdO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 47°. There are a spread of Ti–O bond distances ranging from 1.93–2.04 Å. In the seventh Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra and edges with five GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–49°. There are a spread of Ti–O bond distances ranging from 1.95–1.99 Å. In the eighth Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra and edges with six GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 47–49°. There are a spread of Ti–O bond distances ranging from 1.94–2.01 Å. In the ninth Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra and edges with six GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Ti–O bond distances ranging from 1.98–2.00 Å. In the tenth Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra and edges with four equivalent GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Ti–O bond distances ranging from 1.97–1.99 Å. In the eleventh Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five TiO6 octahedra, a cornercorner with one GdO7 pentagonal bipyramid, edges with three GdO8 hexagonal bipyramids, and an edgeedge with one TiO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 37–54°. There are a spread of Ti–O bond distances ranging from 1.92–2.03 Å. In the twelfth Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five TiO6 octahedra, a cornercorner with one GdO7 pentagonal bipyramid, and edges with four GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Ti–O bond distances ranging from 1.93–2.04 Å. There are forty inequivalent O2- sites. In the first O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form OGd3Ti tetrahedra that share corners with seven OGdTi3 tetrahedra and edges with three OGd3Ti tetrahedra. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Gd3+ and two equivalent Ti4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the fifth O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form OGd3Ti tetrahedra that share corners with ten OGd2Ti2 tetrahedra and an edgeedge with one OGd3Ti tetrahedra. In the sixth O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form OGd3Ti tetrahedra that share corners with six OGd3Ti tetrahedra and edges with three OGd2Ti2 tetrahedra. In the seventh O2- site, O2- is bonded to two Gd3+ and two Ti4+ atoms to form a mixture of distorted corner and edge-sharing OGd2Ti2 tetrahedra. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to two Gd3+ and two equivalent Ti4+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the tenth O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form OGd3Ti tetrahedra that share corners with six OGd3Ti tetrahedra and edges with three OGd2Ti2 tetrahedra. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the thirteenth O2- site, O2- is bonded to four Gd3+ atoms to form corner-sharing OGd4 tetrahedra. In the fourteenth O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form a mixture of distorted corner and edge-sharing OGd3Ti tetrahedra. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Gd3+ and two equivalent Ti4+ atoms. In the sixteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two equivalent Ti4+ atoms. In the seventeenth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the eighteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the nineteenth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Gd3+ and two Ti4+ atoms. In the twentieth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the twenty-first O2- site, O2- is bonded to four Gd3+ atoms to form corner-sharing OGd4 tetrahedra. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the twenty-third O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form OGd3Ti tetrahedra that share corners with six OGd3Ti tetrahedra and edges with three OGd2Ti2 tetrahedra. In the twenty-fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Gd3+ and two Ti4+ atoms. In the twenty-fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Gd3+ and three Ti4+ atoms. In the twenty-sixth O2- site, O2- is bonded to one Gd3+ and three Ti4+ atoms to form distorted OGdTi3 tetrahedra that share corners with two OGd3Ti tetrahedra and edges with three OGd2Ti2 tetrahedra. In the twenty-seventh O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the twenty-eighth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Gd3+ and two Ti4+ atoms. In the twenty-ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the thirtieth O2- site, O2- is bonded to four Gd3+ atoms to form corner-sharing OGd4 tetrahedra. In the thirty-first O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the thirty-second O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the thirty-third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Gd3+ and two Ti4+ atoms. In the thirty-fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two equivalent Ti4+ atoms. In the thirty-fifth O2- site, O2- is bonded to three Gd3+ and one Ti4+ atom to form a mixture of distorted corner and edge-sharing OGd3Ti tetrahedra. In the thirty-sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the thirty-seventh O2- site, O2- is bonded to four Gd3+ atoms to form corner-sharing OGd4 tetrahedra. In the thirty-eighth O2- site, O2- is bo