Mg6BBiO8 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Bi(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. B(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. Bi(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form BiO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Bi(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1) and four equivalent Mg(3) atoms to form OMg5 square pyramids that share corners with four equivalent O(3)Mg2Bi2B2 octahedra, corners with five equivalent O(1)Mg5 square pyramids, edges with four equivalent O(2)Mg5Bi octahedra, and edges with four equivalent O(4)Mg6 octahedra. The corner-sharing octahedral tilt angles are 89°. In the second O site, O(2) is bonded to one Mg(2), four equivalent Mg(3), and one Bi(1) atom to form OMg5Bi octahedra that share corners with six equivalent O(2)Mg5Bi octahedra, edges with four equivalent O(3)Mg2Bi2B2 octahedra, edges with four equivalent O(4)Mg6 octahedra, and edges with four equivalent O(1)Mg5 square pyramids. The corner-sharing octahedral tilt angles range from 0-2°. In the third O site, O(3) is bonded to two equivalent Mg(3), two equivalent B(1), and two equivalent Bi(1) atoms to form OMg2Bi2B2 octahedra that share corners with two equivalent O(4)Mg6 octahedra, corners with four equivalent O(3)Mg2Bi2B2 octahedra, corners with four equivalent O(1)Mg5 square pyramids, edges with four equivalent O(3)Mg2Bi2B2 octahedra, and edges with four equivalent O(2)Mg5Bi octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mg(3) atoms to form OMg6 octahedra that share corners with two equivalent O(3)Mg2Bi2B2 octahedra, corners with four equivalent O(4)Mg6 octahedra, edges with four equivalent O(2)Mg5Bi octahedra, edges with four equivalent O(4)Mg6 octahedra, and edges with four equivalent O(1)Mg5 square pyramids. The corner-sharing octahedra are not tilted.
Mg6BBiO8 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(1) bond lengths are 2.05 Å. All Mg(1)-O(4) bond lengths are 2.22 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Bi(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(2)-O(2) bond lengths are 2.07 Å. All Mg(2)-O(4) bond lengths are 2.22 Å. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Bi(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. The Mg(3)-O(3) bond length is 2.37 Å. The Mg(3)-O(4) bond length is 2.10 Å. Both Mg(3)-O(1) bond lengths are 2.23 Å. Both Mg(3)-O(2) bond lengths are 2.23 Å. B(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. All B(1)-O(3) bond lengths are 2.22 Å. Bi(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form BiO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Bi(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Bi(1)-O(2) bond lengths are 2.41 Å. All Bi(1)-O(3) bond lengths are 2.22 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1) and four equivalent Mg(3) atoms to form OMg5 square pyramids that share corners with four equivalent O(3)Mg2Bi2B2 octahedra, corners with five equivalent O(1)Mg5 square pyramids, edges with four equivalent O(2)Mg5Bi octahedra, and edges with four equivalent O(4)Mg6 octahedra. The corner-sharing octahedral tilt angles are 89°. In the second O site, O(2) is bonded to one Mg(2), four equivalent Mg(3), and one Bi(1) atom to form OMg5Bi octahedra that share corners with six equivalent O(2)Mg5Bi octahedra, edges with four equivalent O(3)Mg2Bi2B2 octahedra, edges with four equivalent O(4)Mg6 octahedra, and edges with four equivalent O(1)Mg5 square pyramids. The corner-sharing octahedral tilt angles range from 0-2°. In the third O site, O(3) is bonded to two equivalent Mg(3), two equivalent B(1), and two equivalent Bi(1) atoms to form OMg2Bi2B2 octahedra that share corners with two equivalent O(4)Mg6 octahedra, corners with four equivalent O(3)Mg2Bi2B2 octahedra, corners with four equivalent O(1)Mg5 square pyramids, edges with four equivalent O(3)Mg2Bi2B2 octahedra, and edges with four equivalent O(2)Mg5Bi octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mg(3) atoms to form OMg6 octahedra that share corners with two equivalent O(3)Mg2Bi2B2 octahedra, corners with four equivalent O(4)Mg6 octahedra, edges with four equivalent O(2)Mg5Bi octahedra, edges with four equivalent O(4)Mg6 octahedra, and edges with four equivalent O(1)Mg5 square pyramids. The corner-sharing octahedra are not tilted.