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 4-coordinate geometry to one Si(1) and 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 three equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to two equivalent Si(2) and four equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), two equivalent Mg(2), four equivalent Mg(3), one Si(1), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Mg(3), three equivalent Mg(1), three equivalent Mg(2), 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 4-coordinate geometry to one Si(1) and three equivalent Si(2) atoms. The Mg(1)-Si(1) bond length is 2.79 Å. There are a spread of Mg(1)-Si(2) bond distances ranging from 2.78-2.85 Å. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Si(1) and three equivalent Si(2) atoms. There is one shorter (2.74 Å) and one longer (3.15 Å) Mg(2)-Si(1) bond length. There are a spread of Mg(2)-Si(2) bond distances ranging from 2.82-3.01 Å. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to two equivalent Si(2) and four equivalent Si(1) atoms. There is one shorter (2.96 Å) and one longer (2.97 Å) Mg(3)-Si(2) bond length. There are a spread of Mg(3)-Si(1) bond distances ranging from 2.74-2.90 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), two equivalent Mg(2), four equivalent Mg(3), one Si(1), and one Si(2) atom. The Si(1)-Si(1) bond length is 2.43 Å. The Si(1)-Si(2) bond length is 2.40 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Mg(3), three equivalent Mg(1), three equivalent Mg(2), and one Si(1) atom.