CaAlTaO5 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(3), and four equivalent O(2) atoms. Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra and corners with four equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. Al(1) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form AlO4 tetrahedra that share corners with four equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-53°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ta(1), and one Al(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Ca(1), one Ta(1), and one Al(1) atom.
CaAlTaO5 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(3), and four equivalent O(2) atoms. The Ca(1)-O(1) bond length is 2.31 Å. Both Ca(1)-O(3) bond lengths are 2.42 Å. There are two shorter (2.44 Å) and two longer (2.72 Å) Ca(1)-O(2) bond lengths. Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra and corners with four equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. Both Ta(1)-O(1) bond lengths are 1.95 Å. Both Ta(1)-O(2) bond lengths are 2.00 Å. Both Ta(1)-O(3) bond lengths are 1.97 Å. Al(1) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form AlO4 tetrahedra that share corners with four equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-53°. Both Al(1)-O(2) bond lengths are 1.76 Å. Both Al(1)-O(3) bond lengths are 1.75 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ta(1), and one Al(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Ca(1), one Ta(1), and one Al(1) atom.