Materials Data on CaAl2B2O7 by Materials Project
CaAl2B2O7 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent O2- atoms to form CaO6 octahedra that share corners with six equivalent AlO4 tetrahedra. All Ca–O bond lengths are 2.40 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent CaO6 octahedra and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. There is one shorter (1.69 Å) and three longer (1.80 Å) Al–O bond length. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.38 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Al3+, and one B3+ atom.