Materials Data on CaAlB3O7 by Materials Project
CaAlB3O7 crystallizes in the orthorhombic Cmme space group. The structure is three-dimensional. Ca2+ is bonded in a q6 geometry to ten O2- atoms. There are a spread of Ca–O bond distances ranging from 2.48–2.64 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six BO4 tetrahedra and edges with two equivalent BO4 tetrahedra. There is two shorter (1.84 Å) and four longer (1.97 Å) Al–O bond length. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with three BO4 tetrahedra, and an edgeedge with one AlO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of B–O bond distances ranging from 1.40–1.56 Å. In the second B3+ site, B3+ is bonded to four equivalent O2- atoms to form BO4 tetrahedra that share corners with four equivalent AlO6 octahedra and corners with four equivalent BO4 tetrahedra. The corner-sharing octahedral tilt angles are 61°. All B–O bond lengths are 1.49 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ca2+, one Al3+, and one B3+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Al3+, and two B3+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent B3+ atoms.