MgHg2(BiO3)4 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(3) and two equivalent O(5) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Bi(2)O6 octahedra, corners with two equivalent Bi(3)O6 octahedra, edges with two equivalent Hg(2)O6 octahedra, and edges with two equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-63°. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form HgO6 octahedra that share corners with four equivalent Bi(3)O6 octahedra, corners with four equivalent Bi(4)O6 octahedra,  an edgeedge with one Bi(1)O6 octahedra, and  an edgeedge with one Bi(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. In the second Hg site, Hg(2) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form distorted HgO6 octahedra that share corners with four equivalent Bi(1)O6 octahedra, corners with four equivalent Bi(2)O6 octahedra,  an edgeedge with one Bi(3)O6 octahedra,  an edgeedge with one Bi(4)O6 octahedra, and edges with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-59°. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form BiO6 octahedra that share corners with four equivalent Hg(2)O6 octahedra, corners with four equivalent Bi(3)O6 octahedra,  an edgeedge with one Hg(1)O6 octahedra,  an edgeedge with one Bi(2)O6 octahedra, and edges with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-53°. In the second Bi site, Bi(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form BiO6 octahedra that share corners with four equivalent Hg(2)O6 octahedra, corners with four equivalent Bi(4)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra,  an edgeedge with one Hg(1)O6 octahedra, and  an edgeedge with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-59°. In the third Bi site, Bi(3) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form BiO6 octahedra that share corners with four equivalent Hg(1)O6 octahedra, corners with four equivalent Bi(1)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra,  an edgeedge with one Hg(2)O6 octahedra, and  an edgeedge with one Bi(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-53°. In the fourth Bi site, Bi(4) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(6) atoms to form BiO6 octahedra that share corners with four equivalent Hg(1)O6 octahedra, corners with four equivalent Bi(2)O6 octahedra,  an edgeedge with one Hg(2)O6 octahedra, and  an edgeedge with one Bi(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-53°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Hg(1), one Bi(2), and one Bi(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Hg(1), one Bi(1), and one Bi(3) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(2), one Bi(1), and one Bi(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Hg(1), one Bi(3), and one Bi(4) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(2), one Bi(1), and one Bi(3) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Hg(2), one Bi(2), and one Bi(4) atom.
MgHg2(BiO3)4 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(3) and two equivalent O(5) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Bi(2)O6 octahedra, corners with two equivalent Bi(3)O6 octahedra, edges with two equivalent Hg(2)O6 octahedra, and edges with two equivalent Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-63°. Both Mg(1)-O(3) bond lengths are 1.96 Å. Both Mg(1)-O(5) bond lengths are 2.01 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form HgO6 octahedra that share corners with four equivalent Bi(3)O6 octahedra, corners with four equivalent Bi(4)O6 octahedra,  an edgeedge with one Bi(1)O6 octahedra, and  an edgeedge with one Bi(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. Both Hg(1)-O(1) bond lengths are 2.36 Å. Both Hg(1)-O(2) bond lengths are 2.41 Å. Both Hg(1)-O(4) bond lengths are 2.38 Å. In the second Hg site, Hg(2) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form distorted HgO6 octahedra that share corners with four equivalent Bi(1)O6 octahedra, corners with four equivalent Bi(2)O6 octahedra,  an edgeedge with one Bi(3)O6 octahedra,  an edgeedge with one Bi(4)O6 octahedra, and edges with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-59°. Both Hg(2)-O(3) bond lengths are 2.42 Å. Both Hg(2)-O(5) bond lengths are 2.47 Å. Both Hg(2)-O(6) bond lengths are 2.28 Å. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form BiO6 octahedra that share corners with four equivalent Hg(2)O6 octahedra, corners with four equivalent Bi(3)O6 octahedra,  an edgeedge with one Hg(1)O6 octahedra,  an edgeedge with one Bi(2)O6 octahedra, and edges with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-53°. Both Bi(1)-O(2) bond lengths are 2.15 Å. Both Bi(1)-O(3) bond lengths are 2.29 Å. Both Bi(1)-O(5) bond lengths are 2.25 Å. In the second Bi site, Bi(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form BiO6 octahedra that share corners with four equivalent Hg(2)O6 octahedra, corners with four equivalent Bi(4)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra,  an edgeedge with one Hg(1)O6 octahedra, and  an edgeedge with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-59°. Both Bi(2)-O(1) bond lengths are 2.17 Å. Both Bi(2)-O(3) bond lengths are 2.29 Å. Both Bi(2)-O(6) bond lengths are 2.23 Å. In the third Bi site, Bi(3) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form BiO6 octahedra that share corners with four equivalent Hg(1)O6 octahedra, corners with four equivalent Bi(1)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra,  an edgeedge with one Hg(2)O6 octahedra, and  an edgeedge with one Bi(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-53°. Both Bi(3)-O(2) bond lengths are 2.21 Å. Both Bi(3)-O(4) bond lengths are 2.19 Å. Both Bi(3)-O(5) bond lengths are 2.30 Å. In the fourth Bi site, Bi(4) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(6) atoms to form BiO6 octahedra that share corners with four equivalent Hg(1)O6 octahedra, corners with four equivalent Bi(2)O6 octahedra,  an edgeedge with one Hg(2)O6 octahedra, and  an edgeedge with one Bi(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-53°. Both Bi(4)-O(1) bond lengths are 2.22 Å. Both Bi(4)-O(4) bond lengths are 2.20 Å. Both Bi(4)-O(6) bond lengths are 2.25 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Hg(1), one Bi(2), and one Bi(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Hg(1), one Bi(1), and one Bi(3) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(2), one Bi(1), and one Bi(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Hg(1), one Bi(3), and one Bi(4) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(2), one Bi(1), and one Bi(3) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Hg(2), one Bi(2), and one Bi(4) atom.