Materials Data on Ca3Ti3(AsO4)4 by Materials Project
Ca3Ti3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.29–2.57 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with four equivalent AsO4 tetrahedra, corners with two equivalent AsO4 trigonal pyramids, and edges with two equivalent TiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.50 Å. There are two 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 equivalent AsO4 tetrahedra, a cornercorner with one AsO4 trigonal pyramid, an edgeedge with one CaO6 octahedra, and an edgeedge with one AsO4 trigonal pyramid. There are a spread of Ti–O bond distances ranging from 1.73–2.19 Å. In the second Ti4+ site, Ti4+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.08 Å) and two longer (2.14 Å) Ti–O bond lengths. There are two inequivalent As+3.50+ sites. In the first As+3.50+ site, As+3.50+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with three equivalent TiO6 octahedra. The corner-sharing octahedra tilt angles range from 44–60°. There are a spread of As–O bond distances ranging from 1.70–1.75 Å. In the second As+3.50+ site, As+3.50+ is bonded to four O2- atoms to form distorted AsO4 trigonal pyramids that share a cornercorner with one CaO6 octahedra, a cornercorner with one TiO6 octahedra, and an edgeedge with one TiO6 octahedra. The corner-sharing octahedra tilt angles range from 61–83°. There are a spread of As–O bond distances ranging from 1.74–2.58 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two Ti4+, and one As+3.50+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Ti4+, and one As+3.50+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Ti4+, and one As+3.50+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, one Ti4+, and one As+3.50+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ca2+ and one As+3.50+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Ti4+, and one As+3.50+ atom. In the seventh O2- site, O2- is bonded to one Ca2+, two Ti4+, and one As+3.50+ atom to form corner-sharing OCaTi2As tetrahedra. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and one As+3.50+ atom.