BaCuO2 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom to form a mixture of corner, edge, and face-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom to form a mixture of corner, edge, and face-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom.
BaCuO2 crystallizes in the monoclinic P2_1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There is one shorter (2.79 Å) and one longer (2.90 Å) Ba(1)-O(1) bond length. There is one shorter (2.70 Å) and one longer (2.73 Å) Ba(1)-O(2) bond length. There is one shorter (2.70 Å) and one longer (2.73 Å) Ba(1)-O(3) bond length. There is one shorter (2.98 Å) and one longer (3.09 Å) Ba(1)-O(4) bond length. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There is one shorter (2.98 Å) and one longer (3.09 Å) Ba(2)-O(1) bond length. There is one shorter (2.70 Å) and one longer (2.73 Å) Ba(2)-O(2) bond length. There is one shorter (2.70 Å) and one longer (2.73 Å) Ba(2)-O(3) bond length. There is one shorter (2.78 Å) and one longer (2.90 Å) Ba(2)-O(4) bond length. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Cu(1)-O(1) bond length is 1.93 Å. The Cu(1)-O(2) bond length is 2.09 Å. The Cu(1)-O(3) bond length is 2.04 Å. The Cu(1)-O(4) bond length is 1.99 Å. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Cu(2)-O(1) bond length is 2.00 Å. The Cu(2)-O(2) bond length is 2.04 Å. The Cu(2)-O(3) bond length is 2.10 Å. The Cu(2)-O(4) bond length is 1.93 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom to form a mixture of corner, edge, and face-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom to form a mixture of corner, edge, and face-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), one Cu(1), and one Cu(2) atom.