Mg3Si2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to six equivalent Si(1) atoms. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to four equivalent Si(1) atoms. Si(1) is bonded in a 9-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), and one Si(1) atom.
Mg3Si2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to six equivalent Si(1) atoms. There are a spread of Mg(1)-Si(1) bond distances ranging from 2.83-3.08 Å. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to four equivalent Si(1) atoms. There are two shorter (2.72 Å) and two longer (2.78 Å) Mg(2)-Si(1) bond lengths. Si(1) is bonded in a 9-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.39 Å.