Mg2Bi3O8 is beta indium sulfide-derived structured and crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Bi(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids, and edges with three equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Mg site, Mg(2) is bonded to one O(4) and three equivalent O(2) atoms to form MgO4 trigonal pyramids that share corners with three equivalent Mg(1)O6 octahedra and corners with nine equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-67°. Bi(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form BiO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids,  an edgeedge with one Mg(1)O6 octahedra, and edges with four equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1) and two equivalent Bi(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), and two equivalent Bi(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Bi(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2) and three equivalent Bi(1) atoms.
Mg2Bi3O8 is beta indium sulfide-derived structured and crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Bi(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids, and edges with three equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. All Mg(1)-O(1) bond lengths are 2.14 Å. All Mg(1)-O(2) bond lengths are 2.27 Å. In the second Mg site, Mg(2) is bonded to one O(4) and three equivalent O(2) atoms to form MgO4 trigonal pyramids that share corners with three equivalent Mg(1)O6 octahedra and corners with nine equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-67°. The Mg(2)-O(4) bond length is 2.02 Å. All Mg(2)-O(2) bond lengths are 2.15 Å. Bi(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form BiO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(2)O4 trigonal pyramids,  an edgeedge with one Mg(1)O6 octahedra, and edges with four equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. The Bi(1)-O(3) bond length is 2.22 Å. The Bi(1)-O(4) bond length is 2.34 Å. Both Bi(1)-O(1) bond lengths are 2.23 Å. Both Bi(1)-O(2) bond lengths are 2.31 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1) and two equivalent Bi(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), and two equivalent Bi(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Bi(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2) and three equivalent Bi(1) atoms.