MgHg3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Hg(1) and eight equivalent Hg(2) atoms to form MgHg12 cuboctahedra that share corners with four equivalent Mg(1)Hg12 cuboctahedra, corners with eight equivalent Hg(1)Mg4Hg8 cuboctahedra, edges with eight equivalent Mg(1)Hg12 cuboctahedra, edges with sixteen equivalent Hg(2)Mg4Hg8 cuboctahedra, faces with four equivalent Mg(1)Hg12 cuboctahedra, faces with six equivalent Hg(1)Mg4Hg8 cuboctahedra, and faces with eight equivalent Hg(2)Mg4Hg8 cuboctahedra. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to four equivalent Mg(1) and eight equivalent Hg(2) atoms to form distorted HgMg4Hg8 cuboctahedra that share corners with four equivalent Hg(1)Mg4Hg8 cuboctahedra, corners with eight equivalent Mg(1)Hg12 cuboctahedra, edges with eight equivalent Hg(1)Mg4Hg8 cuboctahedra, edges with sixteen equivalent Hg(2)Mg4Hg8 cuboctahedra, faces with four equivalent Hg(1)Mg4Hg8 cuboctahedra, faces with six equivalent Mg(1)Hg12 cuboctahedra, and faces with eight equivalent Hg(2)Mg4Hg8 cuboctahedra. In the second Hg site, Hg(2) is bonded to four equivalent Mg(1), four equivalent Hg(1), and four equivalent Hg(2) atoms to form distorted HgMg4Hg8 cuboctahedra that share corners with twelve equivalent Hg(2)Mg4Hg8 cuboctahedra, edges with eight equivalent Mg(1)Hg12 cuboctahedra, edges with eight equivalent Hg(1)Mg4Hg8 cuboctahedra, edges with eight equivalent Hg(2)Mg4Hg8 cuboctahedra, faces with four equivalent Mg(1)Hg12 cuboctahedra, faces with four equivalent Hg(1)Mg4Hg8 cuboctahedra, and faces with ten equivalent Hg(2)Mg4Hg8 cuboctahedra.
MgHg3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Hg(1) and eight equivalent Hg(2) atoms to form MgHg12 cuboctahedra that share corners with four equivalent Mg(1)Hg12 cuboctahedra, corners with eight equivalent Hg(1)Mg4Hg8 cuboctahedra, edges with eight equivalent Mg(1)Hg12 cuboctahedra, edges with sixteen equivalent Hg(2)Mg4Hg8 cuboctahedra, faces with four equivalent Mg(1)Hg12 cuboctahedra, faces with six equivalent Hg(1)Mg4Hg8 cuboctahedra, and faces with eight equivalent Hg(2)Mg4Hg8 cuboctahedra. All Mg(1)-Hg(1) bond lengths are 3.17 Å. All Mg(1)-Hg(2) bond lengths are 3.16 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded to four equivalent Mg(1) and eight equivalent Hg(2) atoms to form distorted HgMg4Hg8 cuboctahedra that share corners with four equivalent Hg(1)Mg4Hg8 cuboctahedra, corners with eight equivalent Mg(1)Hg12 cuboctahedra, edges with eight equivalent Hg(1)Mg4Hg8 cuboctahedra, edges with sixteen equivalent Hg(2)Mg4Hg8 cuboctahedra, faces with four equivalent Hg(1)Mg4Hg8 cuboctahedra, faces with six equivalent Mg(1)Hg12 cuboctahedra, and faces with eight equivalent Hg(2)Mg4Hg8 cuboctahedra. All Hg(1)-Hg(2) bond lengths are 3.16 Å. In the second Hg site, Hg(2) is bonded to four equivalent Mg(1), four equivalent Hg(1), and four equivalent Hg(2) atoms to form distorted HgMg4Hg8 cuboctahedra that share corners with twelve equivalent Hg(2)Mg4Hg8 cuboctahedra, edges with eight equivalent Mg(1)Hg12 cuboctahedra, edges with eight equivalent Hg(1)Mg4Hg8 cuboctahedra, edges with eight equivalent Hg(2)Mg4Hg8 cuboctahedra, faces with four equivalent Mg(1)Hg12 cuboctahedra, faces with four equivalent Hg(1)Mg4Hg8 cuboctahedra, and faces with ten equivalent Hg(2)Mg4Hg8 cuboctahedra. All Hg(2)-Hg(2) bond lengths are 3.17 Å.