HgCd3 crystallizes in the hexagonal P-6m2 space group. Hg(1) is bonded to six equivalent Hg(1) and six equivalent Cd(2) atoms to form HgCd6Hg6 cuboctahedra that share corners with six equivalent Hg(1)Cd6Hg6 cuboctahedra, corners with twelve equivalent Cd(1)Cd12 cuboctahedra, edges with six equivalent Hg(1)Cd6Hg6 cuboctahedra, edges with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra, faces with two equivalent Cd(1)Cd12 cuboctahedra, faces with six equivalent Hg(1)Cd6Hg6 cuboctahedra, and faces with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to six equivalent Cd(1) and six equivalent Cd(2) atoms to form CdCd12 cuboctahedra that share corners with six equivalent Cd(1)Cd12 cuboctahedra, corners with twelve equivalent Hg(1)Cd6Hg6 cuboctahedra, edges with six equivalent Cd(1)Cd12 cuboctahedra, edges with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra, faces with two equivalent Hg(1)Cd6Hg6 cuboctahedra, faces with six equivalent Cd(1)Cd12 cuboctahedra, and faces with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra. In the second Cd site, Cd(2) is bonded to three equivalent Hg(1), three equivalent Cd(1), and six equivalent Cd(2) atoms to form CdCd9Hg3 cuboctahedra that share corners with eighteen equivalent Cd(2)Cd9Hg3 cuboctahedra, edges with six equivalent Hg(1)Cd6Hg6 cuboctahedra, edges with six equivalent Cd(1)Cd12 cuboctahedra, edges with six equivalent Cd(2)Cd9Hg3 cuboctahedra, faces with six equivalent Hg(1)Cd6Hg6 cuboctahedra, faces with six equivalent Cd(1)Cd12 cuboctahedra, and faces with eight equivalent Cd(2)Cd9Hg3 cuboctahedra.
HgCd3 crystallizes in the hexagonal P-6m2 space group. Hg(1) is bonded to six equivalent Hg(1) and six equivalent Cd(2) atoms to form HgCd6Hg6 cuboctahedra that share corners with six equivalent Hg(1)Cd6Hg6 cuboctahedra, corners with twelve equivalent Cd(1)Cd12 cuboctahedra, edges with six equivalent Hg(1)Cd6Hg6 cuboctahedra, edges with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra, faces with two equivalent Cd(1)Cd12 cuboctahedra, faces with six equivalent Hg(1)Cd6Hg6 cuboctahedra, and faces with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra. All Hg(1)-Hg(1) bond lengths are 3.07 Å. All Hg(1)-Cd(2) bond lengths are 3.32 Å. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to six equivalent Cd(1) and six equivalent Cd(2) atoms to form CdCd12 cuboctahedra that share corners with six equivalent Cd(1)Cd12 cuboctahedra, corners with twelve equivalent Hg(1)Cd6Hg6 cuboctahedra, edges with six equivalent Cd(1)Cd12 cuboctahedra, edges with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra, faces with two equivalent Hg(1)Cd6Hg6 cuboctahedra, faces with six equivalent Cd(1)Cd12 cuboctahedra, and faces with twelve equivalent Cd(2)Cd9Hg3 cuboctahedra. All Cd(1)-Cd(1) bond lengths are 3.07 Å. All Cd(1)-Cd(2) bond lengths are 3.23 Å. In the second Cd site, Cd(2) is bonded to three equivalent Hg(1), three equivalent Cd(1), and six equivalent Cd(2) atoms to form CdCd9Hg3 cuboctahedra that share corners with eighteen equivalent Cd(2)Cd9Hg3 cuboctahedra, edges with six equivalent Hg(1)Cd6Hg6 cuboctahedra, edges with six equivalent Cd(1)Cd12 cuboctahedra, edges with six equivalent Cd(2)Cd9Hg3 cuboctahedra, faces with six equivalent Hg(1)Cd6Hg6 cuboctahedra, faces with six equivalent Cd(1)Cd12 cuboctahedra, and faces with eight equivalent Cd(2)Cd9Hg3 cuboctahedra. All Cd(2)-Cd(2) bond lengths are 3.07 Å.