Ce3TaO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one O(3), two equivalent O(1), and four equivalent O(2) atoms to form distorted CeO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Ce(1)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with two equivalent Ce(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. Ta(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Ce(1)O7 pentagonal bipyramids, and edges with four equivalent Ce(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 27°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form a mixture of corner and edge-sharing OCe4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ce(2), two equivalent Ce(1), and one Ta(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ce(1) and two equivalent Ta(1) atoms.
Ce3TaO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one O(3), two equivalent O(1), and four equivalent O(2) atoms to form distorted CeO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Ce(1)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with two equivalent Ce(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. The Ce(1)-O(3) bond length is 2.78 Å. There is one shorter (2.30 Å) and one longer (2.33 Å) Ce(1)-O(1) bond length. There are two shorter (2.44 Å) and two longer (2.47 Å) Ce(1)-O(2) bond lengths. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. All Ce(2)-O(1) bond lengths are 2.41 Å. All Ce(2)-O(2) bond lengths are 2.75 Å. Ta(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Ce(1)O7 pentagonal bipyramids, and edges with four equivalent Ce(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 27°. Both Ta(1)-O(3) bond lengths are 1.99 Å. All Ta(1)-O(2) bond lengths are 2.00 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form a mixture of corner and edge-sharing OCe4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ce(2), two equivalent Ce(1), and one Ta(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ce(1) and two equivalent Ta(1) atoms.