MgHg2(BiO3)2 crystallizes in the trigonal R3 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with three equivalent Hg(1)O6 octahedra, edges with three equivalent Bi(1)O6 octahedra, and  a faceface with one Hg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 36°. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted HgO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Bi(1)O6 octahedra,  a faceface with one Mg(1)O6 octahedra, and  a faceface with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-58°. In the second Hg site, Hg(2) is bonded in a trigonal planar geometry to three equivalent O(1) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted BiO6 octahedra that share corners with three equivalent Hg(1)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra, and  a faceface with one Hg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 58°. In the second Bi site, Bi(2) is bonded in a 3-coordinate geometry to three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(1), one Hg(2), and one Bi(1) atom. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Mg(1), one Hg(1), one Bi(1), and one Bi(2) atom.
MgHg2(BiO3)2 crystallizes in the trigonal R3 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form MgO6 octahedra that share corners with three equivalent Hg(1)O6 octahedra, edges with three equivalent Bi(1)O6 octahedra, and  a faceface with one Hg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 36°. All Mg(1)-O(1) bond lengths are 2.15 Å. All Mg(1)-O(2) bond lengths are 2.19 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted HgO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Bi(1)O6 octahedra,  a faceface with one Mg(1)O6 octahedra, and  a faceface with one Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-58°. All Hg(1)-O(1) bond lengths are 2.48 Å. All Hg(1)-O(2) bond lengths are 2.43 Å. In the second Hg site, Hg(2) is bonded in a trigonal planar geometry to three equivalent O(1) atoms. All Hg(2)-O(1) bond lengths are 2.25 Å. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted BiO6 octahedra that share corners with three equivalent Hg(1)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra, and  a faceface with one Hg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Bi(1)-O(1) bond lengths are 2.33 Å. All Bi(1)-O(2) bond lengths are 2.47 Å. In the second Bi site, Bi(2) is bonded in a 3-coordinate geometry to three equivalent O(2) atoms. All Bi(2)-O(2) bond lengths are 2.18 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Hg(1), one Hg(2), and one Bi(1) atom. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one Mg(1), one Hg(1), one Bi(1), and one Bi(2) atom.