Materials Data on CaUTi2O7 by Materials Project
CaUTi2O7 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ca2+ is bonded to eight O2- atoms to form distorted CaO8 hexagonal bipyramids that share edges with two equivalent CaO8 hexagonal bipyramids, edges with four equivalent UO8 hexagonal bipyramids, and edges with six TiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.26–2.57 Å. U4+ is bonded to eight O2- atoms to form distorted UO8 hexagonal bipyramids that share edges with two equivalent UO8 hexagonal bipyramids, edges with four equivalent CaO8 hexagonal bipyramids, and edges with six TiO6 octahedra. There are a spread of U–O bond distances ranging from 2.17–2.50 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra, edges with two equivalent CaO8 hexagonal bipyramids, and edges with four equivalent UO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 49–51°. All Ti–O bond lengths are 1.98 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra, edges with two equivalent UO8 hexagonal bipyramids, and edges with four equivalent CaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 44–49°. There is two shorter (1.97 Å) and four longer (1.99 Å) Ti–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent U4+ atoms to form corner-sharing OCa2U2 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent U4+ and two equivalent Ti4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ti4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one U4+, and two Ti4+ atoms.