Mg3Hg crystallizes in the trigonal R32 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to one Mg(4), one Hg(1), and two equivalent Hg(2) atoms. In the second Mg site, Mg(2) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Hg(1) atoms. In the third Mg site, Mg(3) is bonded in a 3-coordinate geometry to one Mg(4), one Hg(2), and two equivalent Hg(1) atoms. In the fourth Mg site, Mg(4) is bonded in a 11-coordinate geometry to one Mg(4), one Mg(5), three equivalent Mg(1), three equivalent Mg(3), and three equivalent Hg(1) atoms. In the fifth Mg site, Mg(5) is bonded in a trigonal planar geometry to one Mg(4) and three equivalent Hg(2) atoms. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a distorted q6 geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), and four equivalent Mg(3) atoms. In the second Hg site, Hg(2) is bonded in a 8-coordinate geometry to two equivalent Mg(3), two equivalent Mg(5), and four equivalent Mg(1) atoms.
Mg3Hg crystallizes in the trigonal R32 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to one Mg(4), one Hg(1), and two equivalent Hg(2) atoms. The Mg(1)-Mg(4) bond length is 3.15 Å. The Mg(1)-Hg(1) bond length is 2.94 Å. There is one shorter (2.80 Å) and one longer (3.11 Å) Mg(1)-Hg(2) bond length. In the second Mg site, Mg(2) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Hg(1) atoms. All Mg(2)-Hg(1) bond lengths are 2.92 Å. In the third Mg site, Mg(3) is bonded in a 3-coordinate geometry to one Mg(4), one Hg(2), and two equivalent Hg(1) atoms. The Mg(3)-Mg(4) bond length is 3.10 Å. The Mg(3)-Hg(2) bond length is 2.93 Å. There is one shorter (2.86 Å) and one longer (3.04 Å) Mg(3)-Hg(1) bond length. In the fourth Mg site, Mg(4) is bonded in a 11-coordinate geometry to one Mg(4), one Mg(5), three equivalent Mg(1), three equivalent Mg(3), and three equivalent Hg(1) atoms. The Mg(4)-Mg(4) bond length is 2.94 Å. The Mg(4)-Mg(5) bond length is 3.22 Å. All Mg(4)-Hg(1) bond lengths are 3.02 Å. In the fifth Mg site, Mg(5) is bonded in a trigonal planar geometry to one Mg(4) and three equivalent Hg(2) atoms. All Mg(5)-Hg(2) bond lengths are 2.79 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a distorted q6 geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), and four equivalent Mg(3) atoms. In the second Hg site, Hg(2) is bonded in a 8-coordinate geometry to two equivalent Mg(3), two equivalent Mg(5), and four equivalent Mg(1) atoms.