Ba6Ho2Rh2Al2O15 crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(3), two equivalent O(2), two equivalent O(4), and four equivalent O(1) atoms. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(5), and four equivalent O(1) atoms. In the third Ba site, Ba(3) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(6), and four equivalent O(4) atoms. In the fourth Ba site, Ba(4) is bonded in a 10-coordinate geometry to two equivalent O(3), four equivalent O(4), and four equivalent O(6) atoms. Ho(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form HoO6 octahedra that share corners with three equivalent Rh(1)O5 square pyramids and corners with three equivalent Al(1)O4 tetrahedra. Rh(1) is bonded to one O(3), two equivalent O(4), and two equivalent O(6) atoms to form RhO5 square pyramids that share corners with three equivalent Ho(1)O6 octahedra and  an edgeedge with one Rh(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 3-5°. Al(1) is bonded to one O(2), one O(5), and two equivalent O(1) atoms to form AlO4 tetrahedra that share corners with three equivalent Ho(1)O6 octahedra and  a cornercorner with one Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-29°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a bent 150 degrees geometry to two equivalent Ba(2) and two equivalent Al(1) atoms. In the second O site, O(6) is bonded to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Rh(1) atoms to form distorted OBa4Rh2 octahedra that share corners with four equivalent O(6)Ba4Rh2 octahedra, corners with six equivalent O(4)Ba4HoRh octahedra, edges with four equivalent O(4)Ba4HoRh octahedra, faces with two equivalent O(4)Ba4HoRh octahedra, and faces with two equivalent O(6)Ba4Rh2 octahedra. The corner-sharing octahedral tilt angles range from 2-60°. In the third O site, O(1) is bonded in a 2-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Ho(1), and one Al(1) atom. In the fourth O site, O(2) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), one Ho(1), and one Al(1) atom. In the fifth O site, O(3) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(3), one Ho(1), and one Rh(1) atom. In the sixth O site, O(4) is bonded to one Ba(1), one Ba(4), two equivalent Ba(3), one Ho(1), and one Rh(1) atom to form distorted OBa4HoRh octahedra that share corners with three equivalent O(6)Ba4Rh2 octahedra, corners with six equivalent O(4)Ba4HoRh octahedra, edges with two equivalent O(6)Ba4Rh2 octahedra,  a faceface with one O(6)Ba4Rh2 octahedra, and faces with two equivalent O(4)Ba4HoRh octahedra. The corner-sharing octahedral tilt angles range from 3-73°.
Ba6Ho2Rh2Al2O15 crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(3), two equivalent O(2), two equivalent O(4), and four equivalent O(1) atoms. The Ba(1)-O(3) bond length is 2.68 Å. Both Ba(1)-O(2) bond lengths are 3.06 Å. Both Ba(1)-O(4) bond lengths are 2.79 Å. There are two shorter (2.97 Å) and two longer (3.04 Å) Ba(1)-O(1) bond lengths. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(5), and four equivalent O(1) atoms. Both Ba(2)-O(2) bond lengths are 2.79 Å. Both Ba(2)-O(5) bond lengths are 3.20 Å. All Ba(2)-O(1) bond lengths are 2.94 Å. In the third Ba site, Ba(3) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(6), and four equivalent O(4) atoms. Both Ba(3)-O(1) bond lengths are 3.36 Å. Both Ba(3)-O(3) bond lengths are 3.00 Å. Both Ba(3)-O(6) bond lengths are 2.77 Å. There are two shorter (2.97 Å) and two longer (2.99 Å) Ba(3)-O(4) bond lengths. In the fourth Ba site, Ba(4) is bonded in a 10-coordinate geometry to two equivalent O(3), four equivalent O(4), and four equivalent O(6) atoms. Both Ba(4)-O(3) bond lengths are 3.10 Å. All Ba(4)-O(4) bond lengths are 2.97 Å. There are two shorter (2.91 Å) and two longer (3.03 Å) Ba(4)-O(6) bond lengths. Ho(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form HoO6 octahedra that share corners with three equivalent Rh(1)O5 square pyramids and corners with three equivalent Al(1)O4 tetrahedra. The Ho(1)-O(2) bond length is 2.34 Å. The Ho(1)-O(3) bond length is 2.18 Å. Both Ho(1)-O(1) bond lengths are 2.22 Å. Both Ho(1)-O(4) bond lengths are 2.24 Å. Rh(1) is bonded to one O(3), two equivalent O(4), and two equivalent O(6) atoms to form RhO5 square pyramids that share corners with three equivalent Ho(1)O6 octahedra and  an edgeedge with one Rh(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 3-5°. The Rh(1)-O(3) bond length is 2.04 Å. Both Rh(1)-O(4) bond lengths are 2.03 Å. Both Rh(1)-O(6) bond lengths are 2.09 Å. Al(1) is bonded to one O(2), one O(5), and two equivalent O(1) atoms to form AlO4 tetrahedra that share corners with three equivalent Ho(1)O6 octahedra and  a cornercorner with one Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-29°. The Al(1)-O(2) bond length is 1.79 Å. The Al(1)-O(5) bond length is 1.76 Å. Both Al(1)-O(1) bond lengths are 1.77 Å. There are six inequivalent O sites. In the first O site, O(5) is bonded in a bent 150 degrees geometry to two equivalent Ba(2) and two equivalent Al(1) atoms. In the second O site, O(6) is bonded to two equivalent Ba(3), two equivalent Ba(4), and two equivalent Rh(1) atoms to form distorted OBa4Rh2 octahedra that share corners with four equivalent O(6)Ba4Rh2 octahedra, corners with six equivalent O(4)Ba4HoRh octahedra, edges with four equivalent O(4)Ba4HoRh octahedra, faces with two equivalent O(4)Ba4HoRh octahedra, and faces with two equivalent O(6)Ba4Rh2 octahedra. The corner-sharing octahedral tilt angles range from 2-60°. In the third O site, O(1) is bonded in a 2-coordinate geometry to one Ba(2), one Ba(3), two equivalent Ba(1), one Ho(1), and one Al(1) atom. In the fourth O site, O(2) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(1), one Ho(1), and one Al(1) atom. In the fifth O site, O(3) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(4), two equivalent Ba(3), one Ho(1), and one Rh(1) atom. In the sixth O site, O(4) is bonded to one Ba(1), one Ba(4), two equivalent Ba(3), one Ho(1), and one Rh(1) atom to form distorted OBa4HoRh octahedra that share corners with three equivalent O(6)Ba4Rh2 octahedra, corners with six equivalent O(4)Ba4HoRh octahedra, edges with two equivalent O(6)Ba4Rh2 octahedra,  a faceface with one O(6)Ba4Rh2 octahedra, and faces with two equivalent O(4)Ba4HoRh octahedra. The corner-sharing octahedral tilt angles range from 3-73°.