Ba2HfO4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. Ba(1) is bonded in a 9-coordinate geometry to four equivalent O(1) and five equivalent O(2) atoms. Hf(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form corner-sharing HfO6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent O sites. In the first O site, O(2) is bonded to five equivalent Ba(1) and one Hf(1) atom to form distorted OBa5Hf octahedra that share corners with five equivalent O(2)Ba5Hf octahedra, corners with twelve equivalent O(1)Ba4Hf2 octahedra, edges with eight equivalent O(2)Ba5Hf octahedra, and faces with four equivalent O(1)Ba4Hf2 octahedra. The corner-sharing octahedral tilt angles range from 0-58°. In the second O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Hf(1) atoms to form distorted OBa4Hf2 octahedra that share corners with two equivalent O(1)Ba4Hf2 octahedra, corners with twelve equivalent O(2)Ba5Hf octahedra, edges with two equivalent O(1)Ba4Hf2 octahedra, faces with four equivalent O(1)Ba4Hf2 octahedra, and faces with four equivalent O(2)Ba5Hf octahedra. The corner-sharing octahedral tilt angles range from 0-58°.
Ba2HfO4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. Ba(1) is bonded in a 9-coordinate geometry to four equivalent O(1) and five equivalent O(2) atoms. All Ba(1)-O(1) bond lengths are 2.88 Å. There is one shorter (2.68 Å) and four longer (2.94 Å) Ba(1)-O(2) bond lengths. Hf(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form corner-sharing HfO6 octahedra. The corner-sharing octahedra are not tilted. Both Hf(1)-O(2) bond lengths are 2.10 Å. All Hf(1)-O(1) bond lengths are 2.08 Å. There are two inequivalent O sites. In the first O site, O(2) is bonded to five equivalent Ba(1) and one Hf(1) atom to form distorted OBa5Hf octahedra that share corners with five equivalent O(2)Ba5Hf octahedra, corners with twelve equivalent O(1)Ba4Hf2 octahedra, edges with eight equivalent O(2)Ba5Hf octahedra, and faces with four equivalent O(1)Ba4Hf2 octahedra. The corner-sharing octahedral tilt angles range from 0-58°. In the second O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Hf(1) atoms to form distorted OBa4Hf2 octahedra that share corners with two equivalent O(1)Ba4Hf2 octahedra, corners with twelve equivalent O(2)Ba5Hf octahedra, edges with two equivalent O(1)Ba4Hf2 octahedra, faces with four equivalent O(1)Ba4Hf2 octahedra, and faces with four equivalent O(2)Ba5Hf octahedra. The corner-sharing octahedral tilt angles range from 0-58°.