BaCuAlSnO5 crystallizes in the tetragonal P4mm space group. Ba(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Cu(1) is bonded in a rectangular see-saw-like geometry to four equivalent O(2) atoms. Al(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. Sn(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Al(1) and two equivalent Sn(1) atoms to form OAl2Sn2 tetrahedra that share corners with six equivalent O(2)Ba2Al2Cu2 octahedra, corners with four equivalent O(1)Al2Sn2 tetrahedra,  an edgeedge with one O(2)Ba2Al2Cu2 octahedra, and edges with four equivalent O(1)Al2Sn2 tetrahedra. The corner-sharing octahedral tilt angles range from 1-72°. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Cu(1), and two equivalent Al(1) atoms to form distorted OBa2Al2Cu2 octahedra that share corners with two equivalent O(2)Ba2Al2Cu2 octahedra, corners with six equivalent O(1)Al2Sn2 tetrahedra, edges with two equivalent O(2)Ba2Al2Cu2 octahedra,  an edgeedge with one O(1)Al2Sn2 tetrahedra, and faces with four equivalent O(2)Ba2Al2Cu2 octahedra. The corner-sharing octahedral tilt angles are 6°. In the third O site, O(3) is bonded in a 5-coordinate geometry to four equivalent Ba(1) and one Sn(1) atom.
BaCuAlSnO5 crystallizes in the tetragonal P4mm 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 2.88 Å. All Ba(1)-O(3) bond lengths are 2.90 Å. Cu(1) is bonded in a rectangular see-saw-like geometry to four equivalent O(2) atoms. All Cu(1)-O(2) bond lengths are 1.92 Å. Al(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. All Al(1)-O(1) bond lengths are 2.31 Å. All Al(1)-O(2) bond lengths are 2.28 Å. Sn(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(1) atoms. The Sn(1)-O(3) bond length is 2.04 Å. All Sn(1)-O(1) bond lengths are 2.11 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Al(1) and two equivalent Sn(1) atoms to form OAl2Sn2 tetrahedra that share corners with six equivalent O(2)Ba2Al2Cu2 octahedra, corners with four equivalent O(1)Al2Sn2 tetrahedra,  an edgeedge with one O(2)Ba2Al2Cu2 octahedra, and edges with four equivalent O(1)Al2Sn2 tetrahedra. The corner-sharing octahedral tilt angles range from 1-72°. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Cu(1), and two equivalent Al(1) atoms to form distorted OBa2Al2Cu2 octahedra that share corners with two equivalent O(2)Ba2Al2Cu2 octahedra, corners with six equivalent O(1)Al2Sn2 tetrahedra, edges with two equivalent O(2)Ba2Al2Cu2 octahedra,  an edgeedge with one O(1)Al2Sn2 tetrahedra, and faces with four equivalent O(2)Ba2Al2Cu2 octahedra. The corner-sharing octahedral tilt angles are 6°. In the third O site, O(3) is bonded in a 5-coordinate geometry to four equivalent Ba(1) and one Sn(1) atom.