BaCuO2 crystallizes in the orthorhombic Cmcm space group. Ba(1) is bonded in a 7-coordinate geometry to two equivalent O(2) and five equivalent O(1) atoms. Cu(1) is bonded in a square co-planar geometry to one O(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to five equivalent Ba(1) and one Cu(1) atom to form distorted OBa5Cu octahedra that share corners with four equivalent O(1)Ba5Cu octahedra, corners with seven equivalent O(2)Ba2Cu3 trigonal bipyramids, edges with eight equivalent O(1)Ba5Cu octahedra, and faces with two equivalent O(2)Ba2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 8°. In the second O site, O(2) is bonded to two equivalent Ba(1) and three equivalent Cu(1) atoms to form distorted OBa2Cu3 trigonal bipyramids that share corners with seven equivalent O(1)Ba5Cu octahedra, corners with four equivalent O(2)Ba2Cu3 trigonal bipyramids, edges with two equivalent O(2)Ba2Cu3 trigonal bipyramids, and faces with two equivalent O(1)Ba5Cu octahedra. The corner-sharing octahedral tilt angles range from 0-56°.
BaCuO2 crystallizes in the orthorhombic Cmcm space group. Ba(1) is bonded in a 7-coordinate geometry to two equivalent O(2) and five equivalent O(1) atoms. Both Ba(1)-O(2) bond lengths are 2.73 Å. There is one shorter (2.67 Å) and four longer (2.84 Å) Ba(1)-O(1) bond lengths. Cu(1) is bonded in a square co-planar geometry to one O(1) and three equivalent O(2) atoms. The Cu(1)-O(1) bond length is 1.88 Å. There is one shorter (1.87 Å) and two longer (2.02 Å) Cu(1)-O(2) bond lengths. There are two inequivalent O sites. In the first O site, O(1) is bonded to five equivalent Ba(1) and one Cu(1) atom to form distorted OBa5Cu octahedra that share corners with four equivalent O(1)Ba5Cu octahedra, corners with seven equivalent O(2)Ba2Cu3 trigonal bipyramids, edges with eight equivalent O(1)Ba5Cu octahedra, and faces with two equivalent O(2)Ba2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 8°. In the second O site, O(2) is bonded to two equivalent Ba(1) and three equivalent Cu(1) atoms to form distorted OBa2Cu3 trigonal bipyramids that share corners with seven equivalent O(1)Ba5Cu octahedra, corners with four equivalent O(2)Ba2Cu3 trigonal bipyramids, edges with two equivalent O(2)Ba2Cu3 trigonal bipyramids, and faces with two equivalent O(1)Ba5Cu octahedra. The corner-sharing octahedral tilt angles range from 0-56°.