Ba2AlBi3O8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Al(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(3) and four equivalent O(1) atoms to form distorted BiO5 trigonal bipyramids that share  a cornercorner with one Bi(2)O6 octahedra and corners with four equivalent Bi(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the second Bi site, Bi(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form BiO6 octahedra that share corners with four equivalent Bi(2)O6 octahedra and corners with two equivalent Bi(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Al(1) and two equivalent Bi(1) atoms to form distorted OAl2Bi2 tetrahedra that share corners with two equivalent O(3)Ba4Bi2 octahedra, corners with ten equivalent O(1)Al2Bi2 tetrahedra, and edges with five equivalent O(1)Al2Bi2 tetrahedra. The corner-sharing octahedral tilt angles are 70°. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Bi(2) atoms to form a mixture of corner, face, and edge-sharing OBa4Bi2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Bi(1), and one Bi(2) atom to form distorted OBa4Bi2 octahedra that share corners with five equivalent O(3)Ba4Bi2 octahedra, corners with eight equivalent O(2)Ba4Bi2 octahedra, corners with four equivalent O(1)Al2Bi2 tetrahedra, edges with four equivalent O(3)Ba4Bi2 octahedra, and faces with four equivalent O(2)Ba4Bi2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°.
Ba2AlBi3O8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. All Ba(1)-O(2) bond lengths are 2.94 Å. All Ba(1)-O(3) bond lengths are 3.08 Å. Al(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Al(1)-O(1) bond lengths are 2.50 Å. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(3) and four equivalent O(1) atoms to form distorted BiO5 trigonal bipyramids that share  a cornercorner with one Bi(2)O6 octahedra and corners with four equivalent Bi(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. The Bi(1)-O(3) bond length is 2.36 Å. All Bi(1)-O(1) bond lengths are 2.29 Å. In the second Bi site, Bi(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form BiO6 octahedra that share corners with four equivalent Bi(2)O6 octahedra and corners with two equivalent Bi(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. Both Bi(2)-O(3) bond lengths are 2.41 Å. All Bi(2)-O(2) bond lengths are 2.16 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Al(1) and two equivalent Bi(1) atoms to form distorted OAl2Bi2 tetrahedra that share corners with two equivalent O(3)Ba4Bi2 octahedra, corners with ten equivalent O(1)Al2Bi2 tetrahedra, and edges with five equivalent O(1)Al2Bi2 tetrahedra. The corner-sharing octahedral tilt angles are 70°. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Bi(2) atoms to form a mixture of corner, face, and edge-sharing OBa4Bi2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Bi(1), and one Bi(2) atom to form distorted OBa4Bi2 octahedra that share corners with five equivalent O(3)Ba4Bi2 octahedra, corners with eight equivalent O(2)Ba4Bi2 octahedra, corners with four equivalent O(1)Al2Bi2 tetrahedra, edges with four equivalent O(3)Ba4Bi2 octahedra, and faces with four equivalent O(2)Ba4Bi2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°.