Ba2YMo3O8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with eight equivalent Ba(1)O12 cuboctahedra, faces with five equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Mo(2)O6 octahedra, and faces with four equivalent Mo(1)O5 square pyramids. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(3) and four equivalent O(1) atoms to form MoO5 square pyramids that share  a cornercorner with one Mo(2)O6 octahedra, corners with four equivalent Mo(1)O5 square pyramids, and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the second Mo site, Mo(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MoO6 octahedra that share corners with four equivalent Mo(2)O6 octahedra, corners with two equivalent Mo(1)O5 square pyramids, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), two equivalent Y(1), and two equivalent Mo(1) atoms. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Mo(2) atoms to form a mixture of distorted corner, edge, and face-sharing OBa4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 0-59°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Mo(1), and one Mo(2) atom to form a mixture of distorted corner, edge, and face-sharing OBa4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 0-59°.
Ba2YMo3O8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with eight equivalent Ba(1)O12 cuboctahedra, faces with five equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Mo(2)O6 octahedra, and faces with four equivalent Mo(1)O5 square pyramids. All Ba(1)-O(1) bond lengths are 3.26 Å. All Ba(1)-O(2) bond lengths are 2.90 Å. All Ba(1)-O(3) bond lengths are 2.97 Å. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Y(1)-O(1) bond lengths are 2.52 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(3) and four equivalent O(1) atoms to form MoO5 square pyramids that share  a cornercorner with one Mo(2)O6 octahedra, corners with four equivalent Mo(1)O5 square pyramids, and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. The Mo(1)-O(3) bond length is 2.18 Å. All Mo(1)-O(1) bond lengths are 2.12 Å. In the second Mo site, Mo(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MoO6 octahedra that share corners with four equivalent Mo(2)O6 octahedra, corners with two equivalent Mo(1)O5 square pyramids, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Mo(2)-O(3) bond lengths are 2.05 Å. All Mo(2)-O(2) bond lengths are 2.10 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), two equivalent Y(1), and two equivalent Mo(1) atoms. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Mo(2) atoms to form a mixture of distorted corner, edge, and face-sharing OBa4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 0-59°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Mo(1), and one Mo(2) atom to form a mixture of distorted corner, edge, and face-sharing OBa4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 0-59°.