Li6MgBr8 crystallizes in the cubic Fm-3m space group. Li(1) is bonded to two equivalent Br(1) and four equivalent Br(2) atoms to form LiBr6 octahedra that share corners with six equivalent Li(1)Br6 octahedra, edges with two equivalent Mg(1)Br6 octahedra, and edges with eight equivalent Li(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. Mg(1) is bonded to six equivalent Br(2) atoms to form MgBr6 octahedra that share edges with twelve equivalent Li(1)Br6 octahedra. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded to six equivalent Li(1) atoms to form BrLi6 octahedra that share corners with six equivalent Br(1)Li6 octahedra and edges with twelve equivalent Br(2)Li4Mg square pyramids. The corner-sharing octahedra are not tilted. In the second Br site, Br(2) is bonded to four equivalent Li(1) and one Mg(1) atom to form BrLi4Mg square pyramids that share corners with nine equivalent Br(2)Li4Mg square pyramids, edges with four equivalent Br(1)Li6 octahedra, and edges with four equivalent Br(2)Li4Mg square pyramids.
Li6MgBr8 crystallizes in the cubic Fm-3m space group. Li(1) is bonded to two equivalent Br(1) and four equivalent Br(2) atoms to form LiBr6 octahedra that share corners with six equivalent Li(1)Br6 octahedra, edges with two equivalent Mg(1)Br6 octahedra, and edges with eight equivalent Li(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. Both Li(1)-Br(1) bond lengths are 2.73 Å. All Li(1)-Br(2) bond lengths are 2.73 Å. Mg(1) is bonded to six equivalent Br(2) atoms to form MgBr6 octahedra that share edges with twelve equivalent Li(1)Br6 octahedra. All Mg(1)-Br(2) bond lengths are 2.67 Å. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded to six equivalent Li(1) atoms to form BrLi6 octahedra that share corners with six equivalent Br(1)Li6 octahedra and edges with twelve equivalent Br(2)Li4Mg square pyramids. The corner-sharing octahedra are not tilted. In the second Br site, Br(2) is bonded to four equivalent Li(1) and one Mg(1) atom to form BrLi4Mg square pyramids that share corners with nine equivalent Br(2)Li4Mg square pyramids, edges with four equivalent Br(1)Li6 octahedra, and edges with four equivalent Br(2)Li4Mg square pyramids.