CsMg14HfO15 crystallizes in the orthorhombic Pmm2 space group. Cs(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(10), and two equivalent O(6) atoms. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted square co-planar geometry to two equivalent O(10) and two equivalent O(7) atoms. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), two equivalent O(11), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Hf(1)O5 square pyramids, edges with two equivalent Mg(7)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, and edges with two equivalent Mg(5)O5 square pyramids. The corner-sharing octahedral tilt angles are 4°. In the third Mg site, Mg(3) is bonded to one O(5), one O(6), one O(7), and two equivalent O(10) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(4)O6 octahedra, corners with four equivalent Mg(3)O5 square pyramids,  an edgeedge with one Mg(7)O6 octahedra, and  an edgeedge with one Mg(8)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. In the fourth Mg site, Mg(4) is bonded to one O(4), one O(5), one O(8), one O(9), and two equivalent O(11) atoms to form MgO6 octahedra that share corners with four equivalent Mg(4)O6 octahedra,  a cornercorner with one Mg(3)O5 square pyramid,  an edgeedge with one Mg(7)O6 octahedra,  an edgeedge with one Mg(8)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra,  an edgeedge with one Mg(5)O5 square pyramid, and edges with two equivalent Hf(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 3-12°. In the fifth Mg site, Mg(5) is bonded to one O(8), two equivalent O(1), and two equivalent O(4) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(7)O6 octahedra, corners with two equivalent Mg(5)O5 square pyramids, edges with two equivalent Mg(2)O6 octahedra, and edges with two equivalent Mg(4)O6 octahedra. The corner-sharing octahedra are not tilted. In the sixth Mg site, Mg(6) is bonded in a bent 150 degrees geometry to two equivalent O(4) atoms. In the seventh Mg site, Mg(7) is bonded to one O(6), one O(8), two equivalent O(2), and two equivalent O(5) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(7)O6 octahedra, corners with two equivalent Mg(8)O6 octahedra,  a cornercorner with one Mg(5)O5 square pyramid, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, and edges with two equivalent Mg(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 14-23°. In the eighth Mg site, Mg(8) is bonded to one O(7), one O(9), two equivalent O(3), and two equivalent O(5) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(7)O6 octahedra, corners with two equivalent Mg(8)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with two equivalent Mg(3)O5 square pyramids, and edges with two equivalent Hf(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 14-24°. In the ninth Mg site, Mg(9) is bonded in a rectangular see-saw-like geometry to one O(1), one O(11), and two equivalent O(4) atoms. In the tenth Mg site, Mg(10) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(2), one O(3), and two equivalent O(5) atoms. Hf(1) is bonded to one O(3), two equivalent O(11), and two equivalent O(9) atoms to form HfO5 square pyramids that share corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Hf(1)O5 square pyramids, edges with two equivalent Mg(8)O6 octahedra, and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles are 9°. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one Cs(1), one Mg(2), two equivalent Mg(5), and two equivalent Mg(9) atoms to form distorted OCsMg5 square pyramids that share corners with two equivalent O(1)CsMg5 square pyramids,  a cornercorner with one O(2)Mg5 trigonal bipyramid, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(10)CsMg4 trigonal bipyramids, edges with two equivalent O(8)Mg6 octahedra, edges with two equivalent O(11)HfMg5 square pyramids, and edges with four equivalent O(4)Mg5 trigonal bipyramids. In the second O site, O(2) is bonded to one Mg(2), two equivalent Mg(10), and two equivalent Mg(7) atoms to form distorted OMg5 trigonal bipyramids that share  a cornercorner with one O(1)CsMg5 square pyramid, corners with two equivalent O(3)HfMg4 square pyramids, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(10)CsMg4 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, edges with two equivalent O(8)Mg6 octahedra, edges with four equivalent O(5)Mg6 octahedra, and edges with two equivalent O(11)HfMg5 square pyramids. In the third O site, O(3) is bonded to two equivalent Mg(10), two equivalent Mg(8), and one Hf(1) atom to form distorted OHfMg4 square pyramids that share corners with two equivalent O(3)HfMg4 square pyramids, corners with two equivalent O(10)CsMg4 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, corners with two equivalent O(7)Mg5 trigonal bipyramids, edges with four equivalent O(5)Mg6 octahedra, edges with two equivalent O(9)Hf2Mg3 square pyramids, and edges with two equivalent O(11)HfMg5 square pyramids. In the fourth O site, O(4) is bonded to one Mg(4), one Mg(5), one Mg(6), and two equivalent Mg(9) atoms to form OMg5 trigonal bipyramids that share  a cornercorner with one O(5)Mg6 octahedra,  a cornercorner with one O(9)Hf2Mg3 square pyramid, corners with four equivalent O(4)Mg5 trigonal bipyramids,  an edgeedge with one O(8)Mg6 octahedra, edges with two equivalent O(1)CsMg5 square pyramids, and edges with two equivalent O(11)HfMg5 square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fifth O site, O(5) is bonded to one Mg(3), one Mg(4), one Mg(7), one Mg(8), and two equivalent Mg(10) atoms to form OMg6 octahedra that share corners with four equivalent O(5)Mg6 octahedra,  a cornercorner with one O(4)Mg5 trigonal bipyramid,  an edgeedge with one O(8)Mg6 octahedra,  an edgeedge with one O(9)Hf2Mg3 square pyramid, edges with two equivalent O(3)HfMg4 square pyramids, edges with two equivalent O(11)HfMg5 square pyramids,  an edgeedge with one O(6)Cs2Mg3 trigonal bipyramid,  an edgeedge with one O(7)Mg5 trigonal bipyramid, edges with two equivalent O(10)CsMg4 trigonal bipyramids, and edges with two equivalent O(2)Mg5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 11-20°. In the sixth O site, O(6) is bonded to two equivalent Cs(1), one Mg(7), and two equivalent Mg(3) atoms to form distorted OCs2Mg3 trigonal bipyramids that share  a cornercorner with one O(8)Mg6 octahedra, corners with two equivalent O(1)CsMg5 square pyramids, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, corners with two equivalent O(7)Mg5 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, and edges with four equivalent O(10)CsMg4 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the seventh O site, O(7) is bonded to one Mg(8), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OMg5 trigonal bipyramids that share  a cornercorner with one O(9)Hf2Mg3 square pyramid, corners with two equivalent O(3)HfMg4 square pyramids, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(7)Mg5 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, and edges with four equivalent O(10)CsMg4 trigonal bipyramids. In the eighth O site, O(8) is bonded to one Mg(5), one Mg(7), two equivalent Mg(2), and two equivalent Mg(4) atoms to form OMg6 octahedra that share corners with two equivalent O(8)Mg6 octahedra, corners with two equivalent O(9)Hf2Mg3 square pyramids,  a cornercorner with one O(6)Cs2Mg3 trigonal bipyramid, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(1)CsMg5 square pyramids, edges with four equivalent O(11)HfMg5 square pyramids, edges with two equivalent O(2)Mg5 trigonal bipyramids, and edges with two equivalent O(4)Mg5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 4°. In the ninth O site, O(9) is bonded to one Mg(8), two equivalent Mg(4), and two equivalent Hf(1) atoms to form OHf2Mg3 square pyramids that share corners with two equivalent O(8)Mg6 octahedra, corners with two equivalent O(9)Hf2Mg3 square pyramids,  a cornercorner with one O(7)Mg5 trigonal bipyramid, corners with two equivalent O(4)Mg5 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(3)HfMg4 square pyramids, and edges with four equivalent O(11)HfMg5 square pyramids. The corner-sharing octahedral tilt angles are 2°. In the tenth O site, O(10) is bonded to one Cs(1), one Mg(1), one Mg(10), and two equivalent Mg(3) atoms to form distorted OCsMg4 trigonal bipyramids that share  a cornercorner with one O(1)CsMg5 square pyramid,  a cornercorner with one O(3)HfMg4 square pyramid,  a cornercorner with one O(11)HfMg5 square pyramid,  a cornercorner with one O(2)Mg5 trigonal bipyramid, corners with four equivalent O(10)CsMg4 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(6)Cs2Mg3 trigonal bipyramids, and edges with two equivalent O(7)Mg5 trigonal bipyramids. In the eleventh O site, O(11) is bonded to one Mg(10), one Mg(2), one Mg(9), two equivalent Mg(4), and one Hf(1) atom to form distorted OHfMg5 square pyramids that share corners with four equivalent O(11)HfMg5 square pyramids,  a cornercorner with one O(10)CsMg4 trigonal bipyramid, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(8)Mg6 octahedra,  an edgeedge with one O(1)CsMg5 square pyramid,  an edgeedge with one O(3)HfMg4 square pyramid, edges with two equivalent O(9)Hf2Mg3 square pyramids,  an edgeedge with one O(2)Mg5 trigonal bipyramid, and edges with two equivalent O(4)Mg5 trigonal bipyramids.
CsMg14HfO15 crystallizes in the orthorhombic Pmm2 space group. Cs(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(10), and two equivalent O(6) atoms. The Cs(1)-O(1) bond length is 3.13 Å. Both Cs(1)-O(10) bond lengths are 2.87 Å. Both Cs(1)-O(6) bond lengths are 2.79 Å. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted square co-planar geometry to two equivalent O(10) and two equivalent O(7) atoms. Both Mg(1)-O(10) bond lengths are 1.98 Å. Both Mg(1)-O(7) bond lengths are 2.13 Å. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), two equivalent O(11), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Hf(1)O5 square pyramids, edges with two equivalent Mg(7)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, and edges with two equivalent Mg(5)O5 square pyramids. The corner-sharing octahedral tilt angles are 4°. The Mg(2)-O(1) bond length is 2.19 Å. The Mg(2)-O(2) bond length is 2.01 Å. Both Mg(2)-O(11) bond lengths are 2.15 Å. Both Mg(2)-O(8) bond lengths are 2.08 Å. In the third Mg site, Mg(3) is bonded to one O(5), one O(6), one O(7), and two equivalent O(10) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(4)O6 octahedra, corners with four equivalent Mg(3)O5 square pyramids,  an edgeedge with one Mg(7)O6 octahedra, and  an edgeedge with one Mg(8)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. The Mg(3)-O(5) bond length is 2.31 Å. The Mg(3)-O(6) bond length is 2.06 Å. The Mg(3)-O(7) bond length is 2.14 Å. Both Mg(3)-O(10) bond lengths are 2.09 Å. In the fourth Mg site, Mg(4) is bonded to one O(4), one O(5), one O(8), one O(9), and two equivalent O(11) atoms to form MgO6 octahedra that share corners with four equivalent Mg(4)O6 octahedra,  a cornercorner with one Mg(3)O5 square pyramid,  an edgeedge with one Mg(7)O6 octahedra,  an edgeedge with one Mg(8)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra,  an edgeedge with one Mg(5)O5 square pyramid, and edges with two equivalent Hf(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 3-12°. The Mg(4)-O(4) bond length is 2.34 Å. The Mg(4)-O(5) bond length is 2.18 Å. The Mg(4)-O(8) bond length is 2.02 Å. The Mg(4)-O(9) bond length is 2.19 Å. Both Mg(4)-O(11) bond lengths are 2.09 Å. In the fifth Mg site, Mg(5) is bonded to one O(8), two equivalent O(1), and two equivalent O(4) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(7)O6 octahedra, corners with two equivalent Mg(5)O5 square pyramids, edges with two equivalent Mg(2)O6 octahedra, and edges with two equivalent Mg(4)O6 octahedra. The corner-sharing octahedra are not tilted. The Mg(5)-O(8) bond length is 2.08 Å. Both Mg(5)-O(1) bond lengths are 2.08 Å. Both Mg(5)-O(4) bond lengths are 2.10 Å. In the sixth Mg site, Mg(6) is bonded in a bent 150 degrees geometry to two equivalent O(4) atoms. Both Mg(6)-O(4) bond lengths are 2.21 Å. In the seventh Mg site, Mg(7) is bonded to one O(6), one O(8), two equivalent O(2), and two equivalent O(5) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(7)O6 octahedra, corners with two equivalent Mg(8)O6 octahedra,  a cornercorner with one Mg(5)O5 square pyramid, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, and edges with two equivalent Mg(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 14-23°. The Mg(7)-O(6) bond length is 2.01 Å. The Mg(7)-O(8) bond length is 2.51 Å. Both Mg(7)-O(2) bond lengths are 2.13 Å. Both Mg(7)-O(5) bond lengths are 2.12 Å. In the eighth Mg site, Mg(8) is bonded to one O(7), one O(9), two equivalent O(3), and two equivalent O(5) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(7)O6 octahedra, corners with two equivalent Mg(8)O6 octahedra, edges with two equivalent Mg(4)O6 octahedra, edges with two equivalent Mg(3)O5 square pyramids, and edges with two equivalent Hf(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 14-24°. The Mg(8)-O(7) bond length is 2.01 Å. The Mg(8)-O(9) bond length is 2.44 Å. Both Mg(8)-O(3) bond lengths are 2.13 Å. Both Mg(8)-O(5) bond lengths are 2.11 Å. In the ninth Mg site, Mg(9) is bonded in a rectangular see-saw-like geometry to one O(1), one O(11), and two equivalent O(4) atoms. The Mg(9)-O(1) bond length is 2.08 Å. The Mg(9)-O(11) bond length is 2.18 Å. Both Mg(9)-O(4) bond lengths are 2.08 Å. In the tenth Mg site, Mg(10) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(2), one O(3), and two equivalent O(5) atoms. The Mg(10)-O(10) bond length is 2.00 Å. The Mg(10)-O(11) bond length is 2.69 Å. The Mg(10)-O(2) bond length is 2.04 Å. The Mg(10)-O(3) bond length is 2.28 Å. Both Mg(10)-O(5) bond lengths are 2.11 Å. Hf(1) is bonded to one O(3), two equivalent O(11), and two equivalent O(9) atoms to form HfO5 square pyramids that share corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Hf(1)O5 square pyramids, edges with two equivalent Mg(8)O6 octahedra, and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles are 9°. The Hf(1)-O(3) bond length is 2.01 Å. Both Hf(1)-O(11) bond lengths are 2.06 Å. Both Hf(1)-O(9) bond lengths are 2.08 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one Cs(1), one Mg(2), two equivalent Mg(5), and two equivalent Mg(9) atoms to form distorted OCsMg5 square pyramids that share corners with two equivalent O(1)CsMg5 square pyramids,  a cornercorner with one O(2)Mg5 trigonal bipyramid, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(10)CsMg4 trigonal bipyramids, edges with two equivalent O(8)Mg6 octahedra, edges with two equivalent O(11)HfMg5 square pyramids, and edges with four equivalent O(4)Mg5 trigonal bipyramids. In the second O site, O(2) is bonded to one Mg(2), two equivalent Mg(10), and two equivalent Mg(7) atoms to form distorted OMg5 trigonal bipyramids that share  a cornercorner with one O(1)CsMg5 square pyramid, corners with two equivalent O(3)HfMg4 square pyramids, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(10)CsMg4 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, edges with two equivalent O(8)Mg6 octahedra, edges with four equivalent O(5)Mg6 octahedra, and edges with two equivalent O(11)HfMg5 square pyramids. In the third O site, O(3) is bonded to two equivalent Mg(10), two equivalent Mg(8), and one Hf(1) atom to form distorted OHfMg4 square pyramids that share corners with two equivalent O(3)HfMg4 square pyramids, corners with two equivalent O(10)CsMg4 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, corners with two equivalent O(7)Mg5 trigonal bipyramids, edges with four equivalent O(5)Mg6 octahedra, edges with two equivalent O(9)Hf2Mg3 square pyramids, and edges with two equivalent O(11)HfMg5 square pyramids. In the fourth O site, O(4) is bonded to one Mg(4), one Mg(5), one Mg(6), and two equivalent Mg(9) atoms to form OMg5 trigonal bipyramids that share  a cornercorner with one O(5)Mg6 octahedra,  a cornercorner with one O(9)Hf2Mg3 square pyramid, corners with four equivalent O(4)Mg5 trigonal bipyramids,  an edgeedge with one O(8)Mg6 octahedra, edges with two equivalent O(1)CsMg5 square pyramids, and edges with two equivalent O(11)HfMg5 square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fifth O site, O(5) is bonded to one Mg(3), one Mg(4), one Mg(7), one Mg(8), and two equivalent Mg(10) atoms to form OMg6 octahedra that share corners with four equivalent O(5)Mg6 octahedra,  a cornercorner with one O(4)Mg5 trigonal bipyramid,  an edgeedge with one O(8)Mg6 octahedra,  an edgeedge with one O(9)Hf2Mg3 square pyramid, edges with two equivalent O(3)HfMg4 square pyramids, edges with two equivalent O(11)HfMg5 square pyramids,  an edgeedge with one O(6)Cs2Mg3 trigonal bipyramid,  an edgeedge with one O(7)Mg5 trigonal bipyramid, edges with two equivalent O(10)CsMg4 trigonal bipyramids, and edges with two equivalent O(2)Mg5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 11-20°. In the sixth O site, O(6) is bonded to two equivalent Cs(1), one Mg(7), and two equivalent Mg(3) atoms to form distorted OCs2Mg3 trigonal bipyramids that share  a cornercorner with one O(8)Mg6 octahedra, corners with two equivalent O(1)CsMg5 square pyramids, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, corners with two equivalent O(7)Mg5 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, and edges with four equivalent O(10)CsMg4 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the seventh O site, O(7) is bonded to one Mg(8), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OMg5 trigonal bipyramids that share  a cornercorner with one O(9)Hf2Mg3 square pyramid, corners with two equivalent O(3)HfMg4 square pyramids, corners with two equivalent O(6)Cs2Mg3 trigonal bipyramids, corners with two equivalent O(7)Mg5 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, and edges with four equivalent O(10)CsMg4 trigonal bipyramids. In the eighth O site, O(8) is bonded to one Mg(5), one Mg(7), two equivalent Mg(2), and two equivalent Mg(4) atoms to form OMg6 octahedra that share corners with two equivalent O(8)Mg6 octahedra, corners with two equivalent O(9)Hf2Mg3 square pyramids,  a cornercorner with one O(6)Cs2Mg3 trigonal bipyramid, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(1)CsMg5 square pyramids, edges with four equivalent O(11)HfMg5 square pyramids, edges with two equivalent O(2)Mg5 trigonal bipyramids, and edges with two equivalent O(4)Mg5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 4°. In the ninth O site, O(9) is bonded to one Mg(8), two equivalent Mg(4), and two equivalent Hf(1) atoms to form OHf2Mg3 square pyramids that share corners with two equivalent O(8)Mg6 octahedra, corners with two equivalent O(9)Hf2Mg3 square pyramids,  a cornercorner with one O(7)Mg5 trigonal bipyramid, corners with two equivalent O(4)Mg5 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(3)HfMg4 square pyramids, and edges with four equivalent O(11)HfMg5 square pyramids. The corner-sharing octahedral tilt angles are 2°. In the tenth O site, O(10) is bonded to one Cs(1), one Mg(1), one Mg(10), and two equivalent Mg(3) atoms to form distorted OCsMg4 trigonal bipyramids that share  a cornercorner with one O(1)CsMg5 square pyramid,  a cornercorner with one O(3)HfMg4 square pyramid,  a cornercorner with one O(11)HfMg5 square pyramid,  a cornercorner with one O(2)Mg5 trigonal bipyramid, corners with four equivalent O(10)CsMg4 trigonal bipyramids, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(6)Cs2Mg3 trigonal bipyramids, and edges with two equivalent O(7)Mg5 trigonal bipyramids. In the eleventh O site, O(11) is bonded to one Mg(10), one Mg(2), one Mg(9), two equivalent Mg(4), and one Hf(1) atom to form distorted OHfMg5 square pyramids that share corners with four equivalent O(11)HfMg5 square pyramids,  a cornercorner with one O(10)CsMg4 trigonal bipyramid, edges with two equivalent O(5)Mg6 octahedra, edges with two equivalent O(8)Mg6 octahedra,  an edgeedge with one O(1)CsMg5 square pyramid,  an edgeedge with one O(3)HfMg4 square pyramid, edges with two equivalent O(9)Hf2Mg3 square pyramids,  an edgeedge with one O(2)Mg5 trigonal bipyramid, and edges with two equivalent O(4)Mg5 trigonal bipyramids.