YBaCo2O5 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(1) and eight equivalent O(2) atoms to form distorted BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with eight equivalent Co(1)O5 square pyramids. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. Co(1) is bonded to one O(1) and four equivalent O(2) atoms to form distorted CoO5 square pyramids that share corners with five equivalent Co(1)O5 square pyramids and faces with four equivalent Ba(1)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Co(1) atoms to form a mixture of corner and edge-sharing OBa4Co2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ba(1), two equivalent Y(1), and two equivalent Co(1) atoms.
YBaCo2O5 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(1) and eight equivalent O(2) atoms to form distorted BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with eight equivalent Co(1)O5 square pyramids. All Ba(1)-O(1) bond lengths are 2.76 Å. All Ba(1)-O(2) bond lengths are 3.12 Å. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. All Y(1)-O(2) bond lengths are 2.41 Å. Co(1) is bonded to one O(1) and four equivalent O(2) atoms to form distorted CoO5 square pyramids that share corners with five equivalent Co(1)O5 square pyramids and faces with four equivalent Ba(1)O12 cuboctahedra. The Co(1)-O(1) bond length is 2.01 Å. All Co(1)-O(2) bond lengths are 2.00 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ba(1) and two equivalent Co(1) atoms to form a mixture of corner and edge-sharing OBa4Co2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ba(1), two equivalent Y(1), and two equivalent Co(1) atoms.