Mg6CrBiO8 is Caswellsilverite-derived structured and 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 Cr(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 MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Bi(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 Cr(1)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 0-7°. Cr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Bi(1)O6 octahedra, corners with four equivalent Cr(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. Bi(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form BiO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with four equivalent Bi(1)O6 octahedra, edges with four equivalent Mg(2)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 four equivalent Mg(3), one Cr(1), and one Bi(1) atom to form OMg4CrBi octahedra that share corners with six equivalent O(1)Mg4CrBi octahedra, edges with four equivalent O(4)Mg4Bi2 octahedra, edges with four equivalent O(3)Mg4Cr2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. 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)Mg4Bi2 octahedra, edges with four equivalent O(3)Mg4Cr2 octahedra, and edges with four equivalent O(1)Mg4CrBi octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Cr(1) atoms to form OMg4Cr2 octahedra that share corners with two equivalent O(4)Mg4Bi2 octahedra, corners with four equivalent O(3)Mg4Cr2 octahedra, edges with four equivalent O(3)Mg4Cr2 octahedra, edges with four equivalent O(1)Mg4CrBi octahedra, and edges with four equivalent O(2)Mg6 octahedra. 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 Bi(1) atoms to form OMg4Bi2 octahedra that share corners with two equivalent O(3)Mg4Cr2 octahedra, corners with four equivalent O(4)Mg4Bi2 octahedra, edges with four equivalent O(4)Mg4Bi2 octahedra, edges with four equivalent O(1)Mg4CrBi octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted.
Mg6CrBiO8 is Caswellsilverite-derived structured and 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 Cr(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 2.21 Å. All Mg(1)-O(3) bond lengths are 2.28 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 Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Bi(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 2.25 Å. All Mg(2)-O(4) bond lengths are 2.28 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 Cr(1)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 0-7°. The Mg(3)-O(3) bond length is 2.08 Å. The Mg(3)-O(4) bond length is 2.38 Å. Both Mg(3)-O(1) bond lengths are 2.28 Å. Both Mg(3)-O(2) bond lengths are 2.28 Å. Cr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Bi(1)O6 octahedra, corners with four equivalent Cr(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 Cr(1)-O(1) bond lengths are 2.04 Å. All Cr(1)-O(3) bond lengths are 2.28 Å. Bi(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form BiO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with four equivalent Bi(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Bi(1)-O(1) bond lengths are 2.42 Å. All Bi(1)-O(4) bond lengths are 2.28 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3), one Cr(1), and one Bi(1) atom to form OMg4CrBi octahedra that share corners with six equivalent O(1)Mg4CrBi octahedra, edges with four equivalent O(4)Mg4Bi2 octahedra, edges with four equivalent O(3)Mg4Cr2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. 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)Mg4Bi2 octahedra, edges with four equivalent O(3)Mg4Cr2 octahedra, and edges with four equivalent O(1)Mg4CrBi octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Cr(1) atoms to form OMg4Cr2 octahedra that share corners with two equivalent O(4)Mg4Bi2 octahedra, corners with four equivalent O(3)Mg4Cr2 octahedra, edges with four equivalent O(3)Mg4Cr2 octahedra, edges with four equivalent O(1)Mg4CrBi octahedra, and edges with four equivalent O(2)Mg6 octahedra. 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 Bi(1) atoms to form OMg4Bi2 octahedra that share corners with two equivalent O(3)Mg4Cr2 octahedra, corners with four equivalent O(4)Mg4Bi2 octahedra, edges with four equivalent O(4)Mg4Bi2 octahedra, edges with four equivalent O(1)Mg4CrBi octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted.