Mg2Si crystallizes in the triclinic P-1 space group. There are four 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 3-coordinate geometry to one Si(2) and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 2-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the fourth Mg site, Mg(4) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) 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(3), two equivalent Mg(4), 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(2), two equivalent Mg(3), two equivalent Mg(4), three equivalent Mg(1), and one Si(2) atom.
Mg2Si crystallizes in the triclinic P-1 space group. There are four 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 2.74 Å. There are a spread of Mg(1)-Si(2) bond distances ranging from 2.93-3.15 Å. In the second Mg site, Mg(2) is bonded in a 3-coordinate geometry to one Si(2) and three equivalent Si(1) atoms. The Mg(2)-Si(2) bond length is 2.71 Å. There are a spread of Mg(2)-Si(1) bond distances ranging from 2.84-3.18 Å. In the third Mg site, Mg(3) is bonded in a 2-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. There is one shorter (2.79 Å) and one longer (3.05 Å) Mg(3)-Si(1) bond length. There is one shorter (2.72 Å) and one longer (3.11 Å) Mg(3)-Si(2) bond length. In the fourth Mg site, Mg(4) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. There is one shorter (2.71 Å) and one longer (2.78 Å) Mg(4)-Si(1) bond length. There is one shorter (2.81 Å) and one longer (2.87 Å) Mg(4)-Si(2) bond length. 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(3), two equivalent Mg(4), three equivalent Mg(2), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.41 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), three equivalent Mg(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.48 Å.