CaTa4O14 crystallizes in the trigonal R-3m space group. Ca(1) is bonded to two equivalent O(3) and six equivalent O(1) atoms to form CaO8 hexagonal bipyramids that share edges with six equivalent Ta(2)O6 octahedra. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to six equivalent O(2) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 37°. In the second Ta site, Ta(2) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Ca(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 37-42°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1) and two equivalent Ta(2) atoms. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Ta(1) and one Ta(2) atom. In the third O site, O(3) is bonded in a single-bond geometry to one Ca(1) atom.
CaTa4O14 crystallizes in the trigonal R-3m space group. Ca(1) is bonded to two equivalent O(3) and six equivalent O(1) atoms to form CaO8 hexagonal bipyramids that share edges with six equivalent Ta(2)O6 octahedra. Both Ca(1)-O(3) bond lengths are 2.50 Å. All Ca(1)-O(1) bond lengths are 2.63 Å. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to six equivalent O(2) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 37°. All Ta(1)-O(2) bond lengths are 1.98 Å. In the second Ta site, Ta(2) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Ca(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 37-42°. Both Ta(2)-O(2) bond lengths are 1.99 Å. All Ta(2)-O(1) bond lengths are 1.99 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1) and two equivalent Ta(2) atoms. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Ta(1) and one Ta(2) atom. In the third O site, O(3) is bonded in a single-bond geometry to one Ca(1) atom.