Mg3Si2 crystallizes in the triclinic P-1 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to two equivalent Si(2) and three equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to two equivalent Mg(2), three equivalent Mg(3), one Si(1), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), three equivalent Mg(1), and one Si(1) atom.
Mg3Si2 crystallizes in the triclinic P-1 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Si(2) atoms. There are a spread of Mg(1)-Si(2) bond distances ranging from 2.77-2.91 Å. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. There is one shorter (2.67 Å) and one longer (2.92 Å) Mg(2)-Si(1) bond length. There is one shorter (2.80 Å) and one longer (2.82 Å) Mg(2)-Si(2) bond length. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to two equivalent Si(2) and three equivalent Si(1) atoms. There is one shorter (2.74 Å) and one longer (2.79 Å) Mg(3)-Si(2) bond length. There is one shorter (2.78 Å) and two longer (2.79 Å) Mg(3)-Si(1) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to two equivalent Mg(2), three equivalent Mg(3), one Si(1), and one Si(2) atom. The Si(1)-Si(1) bond length is 2.41 Å. The Si(1)-Si(2) bond length is 2.46 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), three equivalent Mg(1), and one Si(1) atom.