MgSi2 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), two equivalent Si(3), and five equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Si(2), two equivalent Si(3), three equivalent Si(1), and four equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent Mg(2), and three equivalent Si(4) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), five equivalent Mg(1), one Si(2), and two equivalent Si(3) atoms. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(4), and two equivalent Si(2) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to four equivalent Mg(2), one Si(3), one Si(4), and three equivalent Si(1) atoms.
MgSi2 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), two equivalent Si(3), and five equivalent Si(2) atoms. The Mg(1)-Si(1) bond length is 2.81 Å. Both Mg(1)-Si(3) bond lengths are 2.92 Å. There are a spread of Mg(1)-Si(2) bond distances ranging from 2.88-2.90 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to one Si(2), two equivalent Si(3), three equivalent Si(1), and four equivalent Si(4) atoms. The Mg(2)-Si(2) bond length is 2.78 Å. Both Mg(2)-Si(3) bond lengths are 2.99 Å. There are two shorter (2.80 Å) and one longer (3.04 Å) Mg(2)-Si(1) bond length. There are two shorter (2.96 Å) and two longer (3.06 Å) Mg(2)-Si(4) bond lengths. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent Mg(2), and three equivalent Si(4) atoms. There are two shorter (2.44 Å) and one longer (2.59 Å) Si(1)-Si(4) bond length. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), five equivalent Mg(1), one Si(2), and two equivalent Si(3) atoms. The Si(2)-Si(2) bond length is 2.37 Å. Both Si(2)-Si(3) bond lengths are 2.48 Å. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(4), and two equivalent Si(2) atoms. The Si(3)-Si(4) bond length is 2.76 Å. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to four equivalent Mg(2), one Si(3), one Si(4), and three equivalent Si(1) atoms. The Si(4)-Si(4) bond length is 2.41 Å.