Mg2Si3 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 8-coordinate geometry to one Si(1), three equivalent Si(2), and four equivalent Si(3) atoms. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to two equivalent Si(3), three equivalent Si(1), and four equivalent Si(2) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(1), three equivalent Mg(2), one Si(1), one Si(3), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to three equivalent Mg(1), four equivalent Mg(2), one Si(3), and two equivalent Si(1) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), one Si(1), one Si(2), and one Si(3) atom.
Mg2Si3 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 8-coordinate geometry to one Si(1), three equivalent Si(2), and four equivalent Si(3) atoms. The Mg(1)-Si(1) bond length is 2.91 Å. There are two shorter (3.04 Å) and one longer (3.09 Å) Mg(1)-Si(2) bond length. There are two shorter (2.83 Å) and two longer (3.09 Å) Mg(1)-Si(3) bond lengths. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to two equivalent Si(3), three equivalent Si(1), and four equivalent Si(2) atoms. Both Mg(2)-Si(3) bond lengths are 2.83 Å. There is one shorter (2.99 Å) and two longer (3.00 Å) Mg(2)-Si(1) bond lengths. There are a spread of Mg(2)-Si(2) bond distances ranging from 2.75-3.09 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(1), three equivalent Mg(2), one Si(1), one Si(3), and two equivalent Si(2) atoms. The Si(1)-Si(1) bond length is 2.43 Å. The Si(1)-Si(3) bond length is 2.46 Å. Both Si(1)-Si(2) bond lengths are 2.45 Å. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to three equivalent Mg(1), four equivalent Mg(2), one Si(3), and two equivalent Si(1) atoms. The Si(2)-Si(3) bond length is 2.44 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), one Si(1), one Si(2), and one Si(3) atom. The Si(3)-Si(3) bond length is 2.68 Å.