MgSi2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent Mg(1), two equivalent Si(2), three equivalent Si(1), and five equivalent Si(3) atoms to form a mixture of distorted corner, face, and edge-sharing MgMg2Si10 cuboctahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to six equivalent Mg(1) and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to four equivalent Mg(1), two equivalent Si(1), and four equivalent Si(3) atoms. In the third Si site, Si(3) is bonded in a 5-coordinate geometry to five equivalent Mg(1) and two equivalent Si(2) atoms.
MgSi2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent Mg(1), two equivalent Si(2), three equivalent Si(1), and five equivalent Si(3) atoms to form a mixture of distorted corner, face, and edge-sharing MgMg2Si10 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 2.97 Å. Both Mg(1)-Si(2) bond lengths are 2.86 Å. There are two shorter (2.80 Å) and one longer (2.99 Å) Mg(1)-Si(1) bond length. There are a spread of Mg(1)-Si(3) bond distances ranging from 2.79-2.95 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to six equivalent Mg(1) and two equivalent Si(2) atoms. Both Si(1)-Si(2) bond lengths are 2.87 Å. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to four equivalent Mg(1), two equivalent Si(1), and four equivalent Si(3) atoms. All Si(2)-Si(3) bond lengths are 2.72 Å. In the third Si site, Si(3) is bonded in a 5-coordinate geometry to five equivalent Mg(1) and two equivalent Si(2) atoms.