RbKMg14O15 crystallizes in the orthorhombic Pmm2 space group. Rb(1) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(11), and two equivalent O(9) atoms. K(1) is bonded in a 4-coordinate geometry to 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 to one O(1), one O(3), two equivalent O(10), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(6)O6 octahedra, edges with four equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(8)O5 square pyramids, edges with two equivalent Mg(10)O5 trigonal bipyramids, and edges with two equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 5°. In the second Mg site, Mg(2) is bonded to one O(2), two equivalent O(11), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing MgO5 trigonal bipyramids. In the third Mg site, Mg(3) is bonded to one O(4), one O(5), one O(6), one O(7), and two equivalent O(10) atoms to form MgO6 octahedra that share corners with four equivalent Mg(3)O6 octahedra,  a cornercorner with one Mg(4)O5 square pyramid,  an edgeedge with one Mg(6)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra,  an edgeedge with one Mg(8)O5 square pyramid,  an edgeedge with one Mg(7)O5 trigonal bipyramid, edges with two equivalent Mg(10)O5 trigonal bipyramids, and edges with two equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 9-20°. In the fourth Mg site, Mg(4) is bonded to one O(4), one O(8), one O(9), and two equivalent O(11) atoms to form distorted MgO5 square pyramids that share  a cornercorner with one Mg(3)O6 octahedra, corners with four equivalent Mg(4)O5 square pyramids,  an edgeedge with one Mg(6)O6 octahedra, edges with two equivalent Mg(2)O5 trigonal bipyramids, and edges with two equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 15°. In the fifth Mg site, Mg(5) is bonded in a trigonal planar geometry to one O(8) and two equivalent O(4) atoms. In the sixth Mg site, Mg(6) is bonded to one O(7), one O(9), two equivalent O(1), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(6)O6 octahedra,  a cornercorner with one Mg(8)O5 square pyramid, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(4)O5 square pyramids, and edges with four equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 5°. In the seventh Mg site, Mg(7) is bonded to one O(6), two equivalent O(2), and two equivalent O(5) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(8)O5 square pyramids, corners with two equivalent Mg(2)O5 trigonal bipyramids, corners with two equivalent Mg(7)O5 trigonal bipyramids, edges with two equivalent Mg(3)O6 octahedra, and edges with four equivalent Mg(10)O5 trigonal bipyramids. In the eighth Mg site, Mg(8) is bonded to one O(7), two equivalent O(3), and two equivalent O(5) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(6)O6 octahedra, corners with two equivalent Mg(8)O5 square pyramids, corners with two equivalent Mg(7)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, and edges with four equivalent Mg(10)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the ninth Mg site, Mg(9) is bonded to one O(1), one O(10), one O(11), and two equivalent O(4) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Mg(10)O5 trigonal bipyramid,  a cornercorner with one Mg(2)O5 trigonal bipyramid, corners with three equivalent Mg(9)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(6)O6 octahedra, and edges with two equivalent Mg(4)O5 square pyramids. In the tenth Mg site, Mg(10) is bonded to one O(10), one O(2), one O(3), and two equivalent O(5) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Mg(2)O5 trigonal bipyramid,  a cornercorner with one Mg(9)O5 trigonal bipyramid, corners with four equivalent Mg(10)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(8)O5 square pyramids, and edges with two equivalent Mg(7)O5 trigonal bipyramids. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Mg(6), and two equivalent Mg(9) atoms to form OMg5 square pyramids that share  a cornercorner with one O(3)RbMg5 octahedra, corners with two equivalent O(1)Mg5 square pyramids, corners with two equivalent O(9)Rb2Mg3 trigonal bipyramids, edges with two equivalent O(10)KMg5 octahedra, and edges with two equivalent O(7)Mg6 octahedra. The corner-sharing octahedra are not tilted. 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 corners with two equivalent O(10)KMg5 octahedra, corners with two equivalent O(3)RbMg5 octahedra, corners with two equivalent O(6)K2Mg3 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, and edges with four equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles range from 24-62°. In the third O site, O(3) is bonded to one Rb(1), one Mg(1), two equivalent Mg(10), and two equivalent Mg(8) atoms to form ORbMg5 octahedra that share corners with two equivalent O(3)RbMg5 octahedra,  a cornercorner with one O(1)Mg5 square pyramid, corners with two equivalent O(2)Mg5 trigonal bipyramids, corners with two equivalent O(9)Rb2Mg3 trigonal bipyramids, edges with two equivalent O(10)KMg5 octahedra, edges with two equivalent O(7)Mg6 octahedra, and edges with four equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles are 6°. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Mg(3), one Mg(4), one Mg(5), one Mg(6), and two equivalent Mg(9) atoms. In the fifth O site, O(5) is bonded to one Mg(3), one Mg(7), one Mg(8), and two equivalent Mg(10) atoms to form OMg5 square pyramids that share corners with four equivalent O(5)Mg5 square pyramids,  an edgeedge with one O(7)Mg6 octahedra, edges with two equivalent O(10)KMg5 octahedra, edges with two equivalent O(3)RbMg5 octahedra,  an edgeedge with one O(6)K2Mg3 trigonal bipyramid, and edges with two equivalent O(2)Mg5 trigonal bipyramids. In the sixth O site, O(6) is bonded to two equivalent K(1), one Mg(7), and two equivalent Mg(3) atoms to form distorted OK2Mg3 trigonal bipyramids that share corners with two equivalent O(7)Mg6 octahedra, corners with two equivalent O(6)K2Mg3 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, edges with four equivalent O(10)KMg5 octahedra, and edges with two equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles are 6°. In the seventh O site, O(7) is bonded to one Mg(6), one Mg(8), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OMg6 octahedra that share corners with two equivalent O(7)Mg6 octahedra,  a cornercorner with one O(9)Rb2Mg3 trigonal bipyramid, corners with two equivalent O(6)K2Mg3 trigonal bipyramids, edges with two equivalent O(3)RbMg5 octahedra, edges with four equivalent O(10)KMg5 octahedra, edges with two equivalent O(1)Mg5 square pyramids, and edges with two equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles are 5°. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Mg(5), two equivalent Mg(2), and two equivalent Mg(4) atoms. In the ninth O site, O(9) is bonded to two equivalent Rb(1), one Mg(6), and two equivalent Mg(4) atoms to form ORb2Mg3 trigonal bipyramids that share  a cornercorner with one O(7)Mg6 octahedra, corners with two equivalent O(3)RbMg5 octahedra, corners with two equivalent O(1)Mg5 square pyramids, and corners with two equivalent O(9)Rb2Mg3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-54°. In the tenth O site, O(10) is bonded to one K(1), one Mg(1), one Mg(10), one Mg(9), and two equivalent Mg(3) atoms to form OKMg5 octahedra that share corners with four equivalent O(10)KMg5 octahedra,  a cornercorner with one O(2)Mg5 trigonal bipyramid,  an edgeedge with one O(3)RbMg5 octahedra, edges with two equivalent O(7)Mg6 octahedra,  an edgeedge with one O(1)Mg5 square pyramid, edges with two equivalent O(5)Mg5 square pyramids, and edges with two equivalent O(6)K2Mg3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 2-37°. In the eleventh O site, O(11) is bonded in a 5-coordinate geometry to one Rb(1), one Mg(2), one Mg(9), and two equivalent Mg(4) atoms.
RbKMg14O15 crystallizes in the orthorhombic Pmm2 space group. Rb(1) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(11), and two equivalent O(9) atoms. The Rb(1)-O(3) bond length is 2.66 Å. Both Rb(1)-O(11) bond lengths are 2.92 Å. Both Rb(1)-O(9) bond lengths are 2.57 Å. K(1) is bonded in a 4-coordinate geometry to two equivalent O(10) and two equivalent O(6) atoms. Both K(1)-O(10) bond lengths are 2.39 Å. Both K(1)-O(6) bond lengths are 2.43 Å. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(3), two equivalent O(10), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(6)O6 octahedra, edges with four equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(8)O5 square pyramids, edges with two equivalent Mg(10)O5 trigonal bipyramids, and edges with two equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 5°. The Mg(1)-O(1) bond length is 2.07 Å. The Mg(1)-O(3) bond length is 2.09 Å. Both Mg(1)-O(10) bond lengths are 2.02 Å. Both Mg(1)-O(7) bond lengths are 2.09 Å. In the second Mg site, Mg(2) is bonded to one O(2), two equivalent O(11), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing MgO5 trigonal bipyramids. The Mg(2)-O(2) bond length is 2.10 Å. Both Mg(2)-O(11) bond lengths are 2.11 Å. Both Mg(2)-O(8) bond lengths are 2.12 Å. In the third Mg site, Mg(3) is bonded to one O(4), one O(5), one O(6), one O(7), and two equivalent O(10) atoms to form MgO6 octahedra that share corners with four equivalent Mg(3)O6 octahedra,  a cornercorner with one Mg(4)O5 square pyramid,  an edgeedge with one Mg(6)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra,  an edgeedge with one Mg(8)O5 square pyramid,  an edgeedge with one Mg(7)O5 trigonal bipyramid, edges with two equivalent Mg(10)O5 trigonal bipyramids, and edges with two equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 9-20°. The Mg(3)-O(4) bond length is 2.31 Å. The Mg(3)-O(5) bond length is 2.19 Å. The Mg(3)-O(6) bond length is 2.04 Å. The Mg(3)-O(7) bond length is 2.29 Å. Both Mg(3)-O(10) bond lengths are 2.10 Å. In the fourth Mg site, Mg(4) is bonded to one O(4), one O(8), one O(9), and two equivalent O(11) atoms to form distorted MgO5 square pyramids that share  a cornercorner with one Mg(3)O6 octahedra, corners with four equivalent Mg(4)O5 square pyramids,  an edgeedge with one Mg(6)O6 octahedra, edges with two equivalent Mg(2)O5 trigonal bipyramids, and edges with two equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 15°. The Mg(4)-O(4) bond length is 2.18 Å. The Mg(4)-O(8) bond length is 2.31 Å. The Mg(4)-O(9) bond length is 2.06 Å. Both Mg(4)-O(11) bond lengths are 2.14 Å. In the fifth Mg site, Mg(5) is bonded in a trigonal planar geometry to one O(8) and two equivalent O(4) atoms. The Mg(5)-O(8) bond length is 1.95 Å. Both Mg(5)-O(4) bond lengths are 2.00 Å. In the sixth Mg site, Mg(6) is bonded to one O(7), one O(9), two equivalent O(1), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(6)O6 octahedra,  a cornercorner with one Mg(8)O5 square pyramid, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(4)O5 square pyramids, and edges with four equivalent Mg(9)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 5°. The Mg(6)-O(7) bond length is 2.07 Å. The Mg(6)-O(9) bond length is 2.01 Å. Both Mg(6)-O(1) bond lengths are 2.09 Å. Both Mg(6)-O(4) bond lengths are 2.45 Å. In the seventh Mg site, Mg(7) is bonded to one O(6), two equivalent O(2), and two equivalent O(5) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(8)O5 square pyramids, corners with two equivalent Mg(2)O5 trigonal bipyramids, corners with two equivalent Mg(7)O5 trigonal bipyramids, edges with two equivalent Mg(3)O6 octahedra, and edges with four equivalent Mg(10)O5 trigonal bipyramids. The Mg(7)-O(6) bond length is 2.00 Å. Both Mg(7)-O(2) bond lengths are 2.15 Å. Both Mg(7)-O(5) bond lengths are 2.22 Å. In the eighth Mg site, Mg(8) is bonded to one O(7), two equivalent O(3), and two equivalent O(5) atoms to form MgO5 square pyramids that share  a cornercorner with one Mg(6)O6 octahedra, corners with two equivalent Mg(8)O5 square pyramids, corners with two equivalent Mg(7)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, and edges with four equivalent Mg(10)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. The Mg(8)-O(7) bond length is 2.06 Å. Both Mg(8)-O(3) bond lengths are 2.09 Å. Both Mg(8)-O(5) bond lengths are 2.10 Å. In the ninth Mg site, Mg(9) is bonded to one O(1), one O(10), one O(11), and two equivalent O(4) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Mg(10)O5 trigonal bipyramid,  a cornercorner with one Mg(2)O5 trigonal bipyramid, corners with three equivalent Mg(9)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(6)O6 octahedra, and edges with two equivalent Mg(4)O5 square pyramids. The Mg(9)-O(1) bond length is 1.93 Å. The Mg(9)-O(10) bond length is 2.24 Å. The Mg(9)-O(11) bond length is 2.03 Å. Both Mg(9)-O(4) bond lengths are 2.15 Å. In the tenth Mg site, Mg(10) is bonded to one O(10), one O(2), one O(3), and two equivalent O(5) atoms to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Mg(2)O5 trigonal bipyramid,  a cornercorner with one Mg(9)O5 trigonal bipyramid, corners with four equivalent Mg(10)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(8)O5 square pyramids, and edges with two equivalent Mg(7)O5 trigonal bipyramids. The Mg(10)-O(10) bond length is 2.11 Å. The Mg(10)-O(2) bond length is 2.28 Å. The Mg(10)-O(3) bond length is 2.20 Å. Both Mg(10)-O(5) bond lengths are 2.10 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Mg(6), and two equivalent Mg(9) atoms to form OMg5 square pyramids that share  a cornercorner with one O(3)RbMg5 octahedra, corners with two equivalent O(1)Mg5 square pyramids, corners with two equivalent O(9)Rb2Mg3 trigonal bipyramids, edges with two equivalent O(10)KMg5 octahedra, and edges with two equivalent O(7)Mg6 octahedra. The corner-sharing octahedra are not tilted. 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 corners with two equivalent O(10)KMg5 octahedra, corners with two equivalent O(3)RbMg5 octahedra, corners with two equivalent O(6)K2Mg3 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, and edges with four equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles range from 24-62°. In the third O site, O(3) is bonded to one Rb(1), one Mg(1), two equivalent Mg(10), and two equivalent Mg(8) atoms to form ORbMg5 octahedra that share corners with two equivalent O(3)RbMg5 octahedra,  a cornercorner with one O(1)Mg5 square pyramid, corners with two equivalent O(2)Mg5 trigonal bipyramids, corners with two equivalent O(9)Rb2Mg3 trigonal bipyramids, edges with two equivalent O(10)KMg5 octahedra, edges with two equivalent O(7)Mg6 octahedra, and edges with four equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles are 6°. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Mg(3), one Mg(4), one Mg(5), one Mg(6), and two equivalent Mg(9) atoms. In the fifth O site, O(5) is bonded to one Mg(3), one Mg(7), one Mg(8), and two equivalent Mg(10) atoms to form OMg5 square pyramids that share corners with four equivalent O(5)Mg5 square pyramids,  an edgeedge with one O(7)Mg6 octahedra, edges with two equivalent O(10)KMg5 octahedra, edges with two equivalent O(3)RbMg5 octahedra,  an edgeedge with one O(6)K2Mg3 trigonal bipyramid, and edges with two equivalent O(2)Mg5 trigonal bipyramids. In the sixth O site, O(6) is bonded to two equivalent K(1), one Mg(7), and two equivalent Mg(3) atoms to form distorted OK2Mg3 trigonal bipyramids that share corners with two equivalent O(7)Mg6 octahedra, corners with two equivalent O(6)K2Mg3 trigonal bipyramids, corners with two equivalent O(2)Mg5 trigonal bipyramids, edges with four equivalent O(10)KMg5 octahedra, and edges with two equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles are 6°. In the seventh O site, O(7) is bonded to one Mg(6), one Mg(8), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OMg6 octahedra that share corners with two equivalent O(7)Mg6 octahedra,  a cornercorner with one O(9)Rb2Mg3 trigonal bipyramid, corners with two equivalent O(6)K2Mg3 trigonal bipyramids, edges with two equivalent O(3)RbMg5 octahedra, edges with four equivalent O(10)KMg5 octahedra, edges with two equivalent O(1)Mg5 square pyramids, and edges with two equivalent O(5)Mg5 square pyramids. The corner-sharing octahedral tilt angles are 5°. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Mg(5), two equivalent Mg(2), and two equivalent Mg(4) atoms. In the ninth O site, O(9) is bonded to two equivalent Rb(1), one Mg(6), and two equivalent Mg(4) atoms to form ORb2Mg3 trigonal bipyramids that share  a cornercorner with one O(7)Mg6 octahedra, corners with two equivalent O(3)RbMg5 octahedra, corners with two equivalent O(1)Mg5 square pyramids, and corners with two equivalent O(9)Rb2Mg3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-54°. In the tenth O site, O(10) is bonded to one K(1), one Mg(1), one Mg(10), one Mg(9), and two equivalent Mg(3) atoms to form OKMg5 octahedra that share corners with four equivalent O(10)KMg5 octahedra,  a cornercorner with one O(2)Mg5 trigonal bipyramid,  an edgeedge with one O(3)RbMg5 octahedra, edges with two equivalent O(7)Mg6 octahedra,  an edgeedge with one O(1)Mg5 square pyramid, edges with two equivalent O(5)Mg5 square pyramids, and edges with two equivalent O(6)K2Mg3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 2-37°. In the eleventh O site, O(11) is bonded in a 5-coordinate geometry to one Rb(1), one Mg(2), one Mg(9), and two equivalent Mg(4) atoms.