Mg3Si2 crystallizes in the triclinic P-1 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(2), two equivalent Si(1), and two equivalent Si(3) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Si(2), one Si(3), and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a distorted square co-planar geometry to two equivalent Si(1) and two equivalent Si(3) atoms. In the fourth Mg site, Mg(4) is bonded in a distorted rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to two equivalent Si(2) and two equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(3), one Mg(4), two equivalent Mg(1), three equivalent Mg(2), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(4), one Mg(7), two equivalent Mg(5), two equivalent Mg(6), and one Si(3) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), two equivalent Mg(1), and one Si(2) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(4), one Mg(7), three equivalent Mg(5), three equivalent Mg(6), and one Si(4) atom.
Mg3Si2 crystallizes in the triclinic P-1 space group. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(2), two equivalent Si(1), and two equivalent Si(3) atoms. The Mg(1)-Si(2) bond length is 3.00 Å. There is one shorter (2.68 Å) and one longer (2.95 Å) Mg(1)-Si(1) bond length. There is one shorter (2.71 Å) and one longer (2.77 Å) Mg(1)-Si(3) bond length. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Si(2), one Si(3), and three equivalent Si(1) atoms. The Mg(2)-Si(2) bond length is 2.94 Å. The Mg(2)-Si(3) bond length is 2.76 Å. There are a spread of Mg(2)-Si(1) bond distances ranging from 2.79-2.87 Å. In the third Mg site, Mg(3) is bonded in a distorted square co-planar geometry to two equivalent Si(1) and two equivalent Si(3) atoms. Both Mg(3)-Si(1) bond lengths are 2.92 Å. Both Mg(3)-Si(3) bond lengths are 2.83 Å. In the fourth Mg site, Mg(4) is bonded in a distorted rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. The Mg(4)-Si(1) bond length is 2.77 Å. The Mg(4)-Si(2) bond length is 2.84 Å. The Mg(4)-Si(3) bond length is 2.88 Å. The Mg(4)-Si(4) bond length is 2.74 Å. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. The Mg(5)-Si(3) bond length is 2.80 Å. There is one shorter (2.90 Å) and one longer (3.14 Å) Mg(5)-Si(2) bond length. There are a spread of Mg(5)-Si(4) bond distances ranging from 2.71-2.97 Å. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Si(3), two equivalent Si(2), and three equivalent Si(4) atoms. The Mg(6)-Si(3) bond length is 2.88 Å. There is one shorter (2.80 Å) and one longer (2.92 Å) Mg(6)-Si(2) bond length. There are a spread of Mg(6)-Si(4) bond distances ranging from 2.75-3.04 Å. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to two equivalent Si(2) and two equivalent Si(4) atoms. Both Mg(7)-Si(2) bond lengths are 2.67 Å. Both Mg(7)-Si(4) bond lengths are 2.83 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(3), one Mg(4), two equivalent Mg(1), three equivalent Mg(2), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.44 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(4), one Mg(7), two equivalent Mg(5), two equivalent Mg(6), and one Si(3) atom. The Si(2)-Si(3) bond length is 2.41 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), two equivalent Mg(1), and one Si(2) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(4), one Mg(7), three equivalent Mg(5), three equivalent Mg(6), and one Si(4) atom. The Si(4)-Si(4) bond length is 2.42 Å.