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 6-coordinate geometry to one Si(1), one Si(3), two equivalent Si(2), and two equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Si(1), two equivalent Si(4), and four equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to one Mg(1), two equivalent Mg(2), one Si(3), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded to two equivalent Mg(1), one Si(2), and two equivalent Si(1) atoms to form edge-sharing SiMg2Si3 square pyramids. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(1), four equivalent Mg(2), one Si(1), and two equivalent Si(4) atoms. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(4), and two equivalent Si(3) 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 6-coordinate geometry to one Si(1), one Si(3), two equivalent Si(2), and two equivalent Si(4) atoms. The Mg(1)-Si(1) bond length is 3.00 Å. The Mg(1)-Si(3) bond length is 3.00 Å. Both Mg(1)-Si(2) bond lengths are 2.83 Å. Both Mg(1)-Si(4) bond lengths are 2.82 Å. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Si(1), two equivalent Si(4), and four equivalent Si(3) atoms. Both Mg(2)-Si(1) bond lengths are 2.83 Å. There is one shorter (2.73 Å) and one longer (2.94 Å) Mg(2)-Si(4) bond length. There are two shorter (2.94 Å) and two longer (3.10 Å) Mg(2)-Si(3) bond lengths. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to one Mg(1), two equivalent Mg(2), one Si(3), and two equivalent Si(2) atoms. The Si(1)-Si(3) bond length is 2.39 Å. Both Si(1)-Si(2) bond lengths are 2.35 Å. In the second Si site, Si(2) is bonded to two equivalent Mg(1), one Si(2), and two equivalent Si(1) atoms to form edge-sharing SiMg2Si3 square pyramids. The Si(2)-Si(2) bond length is 2.41 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(1), four equivalent Mg(2), one Si(1), and two equivalent Si(4) atoms. Both Si(3)-Si(4) bond lengths are 2.39 Å. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), one Si(4), and two equivalent Si(3) atoms. The Si(4)-Si(4) bond length is 2.39 Å.