CaTa4O11 crystallizes in the hexagonal P6_322 space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1) and six equivalent O(3) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in an octahedral geometry to six equivalent O(3) atoms. In the second Ta site, Ta(2) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1) and three equivalent Ta(2) atoms to form distorted corner-sharing OCaTa3 tetrahedra. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to three equivalent Ta(2) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ta(1), and one Ta(2) atom.
CaTa4O11 crystallizes in the hexagonal P6_322 space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1) and six equivalent O(3) atoms. Both Ca(1)-O(1) bond lengths are 2.66 Å. All Ca(1)-O(3) bond lengths are 2.46 Å. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in an octahedral geometry to six equivalent O(3) atoms. All Ta(1)-O(3) bond lengths are 1.99 Å. In the second Ta site, Ta(2) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. Both Ta(2)-O(1) bond lengths are 2.05 Å. Both Ta(2)-O(3) bond lengths are 1.96 Å. There are two shorter (1.98 Å) and one longer (2.46 Å) Ta(2)-O(2) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1) and three equivalent Ta(2) atoms to form distorted corner-sharing OCaTa3 tetrahedra. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to three equivalent Ta(2) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ta(1), and one Ta(2) atom.