YBa2Fe3O8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form distorted BaO12 cuboctahedra that share corners with eight equivalent Ba(1)O12 cuboctahedra, faces with five equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Fe(2)O6 octahedra, and faces with four equivalent Fe(1)O5 trigonal bipyramids. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3) and four equivalent O(1) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O6 octahedra, corners with four equivalent Fe(1)O5 trigonal bipyramids, and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the second Fe site, Fe(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), two equivalent Y(1), and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Fe(2) atoms to form a mixture of distorted edge, corner, and face-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-55°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Fe(1), and one Fe(2) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-55°.
YBa2Fe3O8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form distorted BaO12 cuboctahedra that share corners with eight equivalent Ba(1)O12 cuboctahedra, faces with five equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Fe(2)O6 octahedra, and faces with four equivalent Fe(1)O5 trigonal bipyramids. All Ba(1)-O(1) bond lengths are 3.33 Å. All Ba(1)-O(2) bond lengths are 2.79 Å. All Ba(1)-O(3) bond lengths are 2.82 Å. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Y(1)-O(1) bond lengths are 2.43 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3) and four equivalent O(1) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O6 octahedra, corners with four equivalent Fe(1)O5 trigonal bipyramids, and faces with four equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. The Fe(1)-O(3) bond length is 1.87 Å. All Fe(1)-O(1) bond lengths are 2.06 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(1)O5 trigonal bipyramids, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Fe(2)-O(3) bond lengths are 2.23 Å. All Fe(2)-O(2) bond lengths are 1.98 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), two equivalent Y(1), and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Fe(2) atoms to form a mixture of distorted edge, corner, and face-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-55°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Fe(1), and one Fe(2) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-55°.