Mg6YBO8 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(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Y(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 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 a mixture of edge and corner-sharing MgO6 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 distorted 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 Y(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. Y(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form YO6 octahedra that share corners with four equivalent Y(1)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. B(1) is bonded in a distorted square co-planar geometry to four equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3) and one Y(1) atom to form distorted OYMg4 square pyramids that share corners with four equivalent O(4)Mg4B2 octahedra, corners with five equivalent O(1)YMg4 square pyramids, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(3)Y2Mg4 octahedra. The corner-sharing octahedral tilt angles are 83°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, edges with four equivalent O(3)Y2Mg4 octahedra, and edges with four equivalent O(1)YMg4 square pyramids. The corner-sharing octahedral tilt angles range from 0-12°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Y(1) atoms to form OY2Mg4 octahedra that share corners with two equivalent O(4)Mg4B2 octahedra, corners with four equivalent O(3)Y2Mg4 octahedra, edges with four equivalent O(2)Mg6 octahedra, edges with four equivalent O(3)Y2Mg4 octahedra, and edges with four equivalent O(1)YMg4 square pyramids. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent B(1) atoms to form OMg4B2 octahedra that share corners with two equivalent O(3)Y2Mg4 octahedra, corners with four equivalent O(4)Mg4B2 octahedra, corners with four equivalent O(1)YMg4 square pyramids, edges with four equivalent O(4)Mg4B2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted.
Mg6YBO8 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(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Y(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(2) bond lengths are 2.27 Å. All Mg(1)-O(3) bond lengths are 2.19 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2) 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(2)-O(2) bond lengths are 2.25 Å. All Mg(2)-O(4) bond lengths are 2.19 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 distorted 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 Y(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. The Mg(3)-O(3) bond length is 2.49 Å. The Mg(3)-O(4) bond length is 2.03 Å. Both Mg(3)-O(1) bond lengths are 2.20 Å. Both Mg(3)-O(2) bond lengths are 2.20 Å. Y(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form YO6 octahedra that share corners with four equivalent Y(1)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 Y(1)-O(1) bond lengths are 2.21 Å. All Y(1)-O(3) bond lengths are 2.19 Å. B(1) is bonded in a distorted square co-planar geometry to four equivalent O(4) atoms. All B(1)-O(4) bond lengths are 2.19 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3) and one Y(1) atom to form distorted OYMg4 square pyramids that share corners with four equivalent O(4)Mg4B2 octahedra, corners with five equivalent O(1)YMg4 square pyramids, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(3)Y2Mg4 octahedra. The corner-sharing octahedral tilt angles are 83°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, edges with four equivalent O(3)Y2Mg4 octahedra, and edges with four equivalent O(1)YMg4 square pyramids. The corner-sharing octahedral tilt angles range from 0-12°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Y(1) atoms to form OY2Mg4 octahedra that share corners with two equivalent O(4)Mg4B2 octahedra, corners with four equivalent O(3)Y2Mg4 octahedra, edges with four equivalent O(2)Mg6 octahedra, edges with four equivalent O(3)Y2Mg4 octahedra, and edges with four equivalent O(1)YMg4 square pyramids. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent B(1) atoms to form OMg4B2 octahedra that share corners with two equivalent O(3)Y2Mg4 octahedra, corners with four equivalent O(4)Mg4B2 octahedra, corners with four equivalent O(1)YMg4 square pyramids, edges with four equivalent O(4)Mg4B2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted.