Mg4Si3 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(1) and four equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to two equivalent Si(1) and three equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent Mg(1) and four equivalent Mg(2) atoms to form distorted edge-sharing SiMg6 octahedra. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to three equivalent Mg(2), four equivalent Mg(1), and one Si(2) atom.
Mg4Si3 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(1) and four equivalent Si(2) atoms. The Mg(1)-Si(1) bond length is 2.62 Å. There are a spread of Mg(1)-Si(2) bond distances ranging from 2.78-3.02 Å. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to two equivalent Si(1) and three equivalent Si(2) atoms. There is one shorter (2.68 Å) and one longer (2.73 Å) Mg(2)-Si(1) bond length. There are a spread of Mg(2)-Si(2) bond distances ranging from 2.79-2.84 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent Mg(1) and four equivalent Mg(2) atoms to form distorted edge-sharing SiMg6 octahedra. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to three equivalent Mg(2), four equivalent Mg(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.63 Å.