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 3-coordinate geometry to one Si(1) and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to two equivalent Si(2) and three equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. In the fourth Mg site, Mg(4) is bonded in a 3-coordinate geometry to one 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 8-coordinate geometry to one Mg(1), one Mg(4), two equivalent Mg(3), three equivalent Mg(2), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(4) atoms.
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 3-coordinate geometry to one Si(1) and two equivalent Si(2) atoms. The Mg(1)-Si(1) bond length is 2.72 Å. There is one shorter (2.66 Å) and one longer (2.77 Å) Mg(1)-Si(2) bond length. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to two equivalent Si(2) and three equivalent Si(1) atoms. There is one shorter (2.73 Å) and one longer (2.79 Å) Mg(2)-Si(2) bond length. There are a spread of Mg(2)-Si(1) bond distances ranging from 2.78-2.94 Å. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to two equivalent Si(1) and two equivalent Si(2) atoms. There is one shorter (2.82 Å) and one longer (2.97 Å) Mg(3)-Si(1) bond length. There is one shorter (2.80 Å) and one longer (2.81 Å) Mg(3)-Si(2) bond length. In the fourth Mg site, Mg(4) is bonded in a 3-coordinate geometry to one Si(1) and two equivalent Si(2) atoms. The Mg(4)-Si(1) bond length is 2.78 Å. There is one shorter (2.67 Å) and one longer (2.73 Å) Mg(4)-Si(2) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(4), two equivalent Mg(3), three equivalent Mg(2), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.43 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(4) atoms.