Ba5Ho8Zn4O21 crystallizes in the tetragonal I4/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(2), four equivalent O(1), and four equivalent O(3) atoms. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to two equivalent O(4) and eight equivalent O(2) atoms. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(4), two equivalent O(1), and four equivalent O(2) atoms to form distorted HoO7 pentagonal bipyramids that share  a cornercorner with one Ho(1)O7 pentagonal bipyramid, corners with two equivalent Zn(1)O5 trigonal bipyramids, edges with two equivalent Zn(1)O5 trigonal bipyramids, and faces with two equivalent Ho(1)O7 pentagonal bipyramids. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(2), and four equivalent O(1) atoms. Zn(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted ZnO5 trigonal bipyramids that share corners with two equivalent Ho(1)O7 pentagonal bipyramids and edges with two equivalent Ho(1)O7 pentagonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Ho(1), two equivalent Ho(2), and one Zn(1) atom. In the second O site, O(2) is bonded to one Ba(1), one Ba(2), one Ho(2), two equivalent Ho(1), and one Zn(1) atom to form distorted OBa2Ho3Zn octahedra that share  a cornercorner with one O(4)Ba2Ho4 octahedra, corners with three equivalent O(3)Ba4HoZn octahedra, corners with six equivalent O(2)Ba2Ho3Zn octahedra, edges with two equivalent O(2)Ba2Ho3Zn octahedra,  a faceface with one O(4)Ba2Ho4 octahedra,  a faceface with one O(3)Ba4HoZn octahedra, and faces with two equivalent O(2)Ba2Ho3Zn octahedra. The corner-sharing octahedral tilt angles range from 0-76°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Ho(2), and one Zn(1) atom to form distorted OBa4HoZn octahedra that share corners with two equivalent O(3)Ba4HoZn octahedra, corners with six equivalent O(2)Ba2Ho3Zn octahedra, edges with five equivalent O(3)Ba4HoZn octahedra, and faces with two equivalent O(2)Ba2Ho3Zn octahedra. The corner-sharing octahedral tilt angles range from 6-59°. In the fourth O site, O(4) is bonded to two equivalent Ba(2) and four equivalent Ho(1) atoms to form OBa2Ho4 octahedra that share corners with two equivalent O(4)Ba2Ho4 octahedra, corners with eight equivalent O(2)Ba2Ho3Zn octahedra, and faces with eight equivalent O(2)Ba2Ho3Zn octahedra. The corner-sharing octahedral tilt angles range from 0-61°.
Ba5Ho8Zn4O21 crystallizes in the tetragonal I4/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(2), four equivalent O(1), and four equivalent O(3) atoms. Both Ba(1)-O(2) bond lengths are 2.92 Å. There are two shorter (3.21 Å) and two longer (3.26 Å) Ba(1)-O(1) bond lengths. There are a spread of Ba(1)-O(3) bond distances ranging from 2.67-2.87 Å. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to two equivalent O(4) and eight equivalent O(2) atoms. Both Ba(2)-O(4) bond lengths are 2.87 Å. All Ba(2)-O(2) bond lengths are 2.93 Å. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(4), two equivalent O(1), and four equivalent O(2) atoms to form distorted HoO7 pentagonal bipyramids that share  a cornercorner with one Ho(1)O7 pentagonal bipyramid, corners with two equivalent Zn(1)O5 trigonal bipyramids, edges with two equivalent Zn(1)O5 trigonal bipyramids, and faces with two equivalent Ho(1)O7 pentagonal bipyramids. The Ho(1)-O(4) bond length is 2.32 Å. Both Ho(1)-O(1) bond lengths are 2.31 Å. There are two shorter (2.29 Å) and two longer (2.43 Å) Ho(1)-O(2) bond lengths. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(2), and four equivalent O(1) atoms. The Ho(2)-O(3) bond length is 2.49 Å. Both Ho(2)-O(2) bond lengths are 2.40 Å. There are two shorter (2.29 Å) and two longer (2.33 Å) Ho(2)-O(1) bond lengths. Zn(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted ZnO5 trigonal bipyramids that share corners with two equivalent Ho(1)O7 pentagonal bipyramids and edges with two equivalent Ho(1)O7 pentagonal bipyramids. The Zn(1)-O(3) bond length is 2.00 Å. Both Zn(1)-O(1) bond lengths are 2.07 Å. Both Zn(1)-O(2) bond lengths are 2.14 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Ho(1), two equivalent Ho(2), and one Zn(1) atom. In the second O site, O(2) is bonded to one Ba(1), one Ba(2), one Ho(2), two equivalent Ho(1), and one Zn(1) atom to form distorted OBa2Ho3Zn octahedra that share  a cornercorner with one O(4)Ba2Ho4 octahedra, corners with three equivalent O(3)Ba4HoZn octahedra, corners with six equivalent O(2)Ba2Ho3Zn octahedra, edges with two equivalent O(2)Ba2Ho3Zn octahedra,  a faceface with one O(4)Ba2Ho4 octahedra,  a faceface with one O(3)Ba4HoZn octahedra, and faces with two equivalent O(2)Ba2Ho3Zn octahedra. The corner-sharing octahedral tilt angles range from 0-76°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Ho(2), and one Zn(1) atom to form distorted OBa4HoZn octahedra that share corners with two equivalent O(3)Ba4HoZn octahedra, corners with six equivalent O(2)Ba2Ho3Zn octahedra, edges with five equivalent O(3)Ba4HoZn octahedra, and faces with two equivalent O(2)Ba2Ho3Zn octahedra. The corner-sharing octahedral tilt angles range from 6-59°. In the fourth O site, O(4) is bonded to two equivalent Ba(2) and four equivalent Ho(1) atoms to form OBa2Ho4 octahedra that share corners with two equivalent O(4)Ba2Ho4 octahedra, corners with eight equivalent O(2)Ba2Ho3Zn octahedra, and faces with eight equivalent O(2)Ba2Ho3Zn octahedra. The corner-sharing octahedral tilt angles range from 0-61°.