MgSi2 crystallizes in the monoclinic P2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 9-coordinate geometry to two equivalent Mg(2), one Si(2), two equivalent Si(1), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(5) atoms. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to one Mg(2), two equivalent Mg(1), one Si(1), one Si(4), one Si(5), two equivalent Si(3), and four equivalent Si(2) atoms. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), and four equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), four equivalent Mg(2), two equivalent Si(4), and two equivalent Si(5) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Si(1), and two equivalent Si(4) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(1), one Si(4), two equivalent Si(2), and two equivalent Si(3) atoms. In the fifth Si site, Si(5) is bonded in a distorted q6 geometry to two equivalent Mg(2), four equivalent Mg(1), and four equivalent Si(2) atoms.
MgSi2 crystallizes in the monoclinic P2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 9-coordinate geometry to two equivalent Mg(2), one Si(2), two equivalent Si(1), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(5) atoms. Both Mg(1)-Mg(2) bond lengths are 3.04 Å. The Mg(1)-Si(2) bond length is 2.67 Å. Both Mg(1)-Si(1) bond lengths are 2.83 Å. There is one shorter (2.80 Å) and one longer (2.99 Å) Mg(1)-Si(3) bond length. Both Mg(1)-Si(4) bond lengths are 3.00 Å. Both Mg(1)-Si(5) bond lengths are 2.91 Å. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to one Mg(2), two equivalent Mg(1), one Si(1), one Si(4), one Si(5), two equivalent Si(3), and four equivalent Si(2) atoms. The Mg(2)-Mg(2) bond length is 2.90 Å. The Mg(2)-Si(1) bond length is 3.16 Å. The Mg(2)-Si(4) bond length is 2.80 Å. The Mg(2)-Si(5) bond length is 3.04 Å. Both Mg(2)-Si(3) bond lengths are 2.79 Å. There are two shorter (2.90 Å) and two longer (3.02 Å) Mg(2)-Si(2) bond lengths. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to two equivalent Mg(2), four equivalent Mg(1), and four equivalent Si(3) atoms. All Si(1)-Si(3) bond lengths are 2.54 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), four equivalent Mg(2), two equivalent Si(4), and two equivalent Si(5) atoms. Both Si(2)-Si(4) bond lengths are 2.73 Å. Both Si(2)-Si(5) bond lengths are 2.59 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Si(1), and two equivalent Si(4) atoms. Both Si(3)-Si(4) bond lengths are 2.53 Å. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(1), one Si(4), two equivalent Si(2), and two equivalent Si(3) atoms. The Si(4)-Si(4) bond length is 2.62 Å. In the fifth Si site, Si(5) is bonded in a distorted q6 geometry to two equivalent Mg(2), four equivalent Mg(1), and four equivalent Si(2) atoms.