BaNiCuAlO5 crystallizes in the tetragonal P4mm space group. Ba(1) is bonded in a distorted square co-planar geometry to four equivalent O(3) atoms. Ni(1) is bonded to one O(3) and four equivalent O(1) atoms to form distorted NiO5 trigonal bipyramids that share  a cornercorner with one Cu(1)O5 trigonal bipyramid and corners with four equivalent Ni(1)O5 trigonal bipyramids. Cu(1) is bonded to one O(3) and four equivalent O(2) atoms to form distorted CuO5 trigonal bipyramids that share  a cornercorner with one Ni(1)O5 trigonal bipyramid and corners with four equivalent Cu(1)O5 trigonal bipyramids. Al(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ni(1) and two equivalent Al(1) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Cu(1) and two equivalent Al(1) atoms. In the third O site, O(3) is bonded to four equivalent Ba(1), one Ni(1), and one Cu(1) atom to form a mixture of edge and corner-sharing OBa4CuNi octahedra. The corner-sharing octahedral tilt angles are 8°.
BaNiCuAlO5 crystallizes in the tetragonal P4mm space group. Ba(1) is bonded in a distorted square co-planar geometry to four equivalent O(3) atoms. All Ba(1)-O(3) bond lengths are 2.63 Å. Ni(1) is bonded to one O(3) and four equivalent O(1) atoms to form distorted NiO5 trigonal bipyramids that share  a cornercorner with one Cu(1)O5 trigonal bipyramid and corners with four equivalent Ni(1)O5 trigonal bipyramids. The Ni(1)-O(3) bond length is 2.01 Å. All Ni(1)-O(1) bond lengths are 1.93 Å. Cu(1) is bonded to one O(3) and four equivalent O(2) atoms to form distorted CuO5 trigonal bipyramids that share  a cornercorner with one Ni(1)O5 trigonal bipyramid and corners with four equivalent Cu(1)O5 trigonal bipyramids. The Cu(1)-O(3) bond length is 2.24 Å. All Cu(1)-O(2) bond lengths are 1.91 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 2.15 Å. All Al(1)-O(2) bond lengths are 2.29 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ni(1) and two equivalent Al(1) atoms. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Cu(1) and two equivalent Al(1) atoms. In the third O site, O(3) is bonded to four equivalent Ba(1), one Ni(1), and one Cu(1) atom to form a mixture of edge and corner-sharing OBa4CuNi octahedra. The corner-sharing octahedral tilt angles are 8°.