MgSi2 crystallizes in the monoclinic Pm space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Si(2), one Si(8), two equivalent Si(1), and two equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to one Si(1), one Si(5), one Si(7), two equivalent Si(2), two equivalent Si(3), and two equivalent Si(8) atoms. In the third Mg site, Mg(3) is bonded to one Si(1), one Si(6), two equivalent Si(2), and two equivalent Si(4) atoms to form distorted edge-sharing MgSi6 octahedra. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one Si(3), one Si(4), one Si(8), two equivalent Si(1), and two equivalent Si(5) atoms. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), two equivalent Mg(1), two equivalent Mg(4), and two equivalent Si(8) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(1), two equivalent Mg(2), two equivalent Mg(3), one Si(3), and two equivalent Si(7) atoms. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to one Mg(4), two equivalent Mg(2), one Si(2), and two equivalent Si(6) atoms. In the fourth Si site, Si(4) is bonded in a 6-coordinate geometry to one Mg(4), two equivalent Mg(3), one Si(8), and two equivalent Si(5) atoms. In the fifth Si site, Si(5) is bonded in a 6-coordinate geometry to one Mg(2), two equivalent Mg(4), one Si(7), two equivalent Si(4), and two equivalent Si(8) atoms. In the sixth Si site, Si(6) is bonded to one Mg(3), two equivalent Mg(1), one Si(7), and two equivalent Si(3) atoms to form distorted edge-sharing SiMg3Si3 octahedra. In the seventh Si site, Si(7) is bonded in a 5-coordinate geometry to one Mg(2), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the eighth Si site, Si(8) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), two equivalent Mg(2), one Si(4), two equivalent Si(1), and two equivalent Si(5) atoms.
MgSi2 crystallizes in the monoclinic Pm space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Si(2), one Si(8), two equivalent Si(1), and two equivalent Si(6) atoms. The Mg(1)-Si(2) bond length is 2.74 Å. The Mg(1)-Si(8) bond length is 2.65 Å. Both Mg(1)-Si(1) bond lengths are 2.89 Å. Both Mg(1)-Si(6) bond lengths are 2.82 Å. In the second Mg site, Mg(2) is bonded in a 9-coordinate geometry to one Si(1), one Si(5), one Si(7), two equivalent Si(2), two equivalent Si(3), and two equivalent Si(8) atoms. The Mg(2)-Si(1) bond length is 2.82 Å. The Mg(2)-Si(5) bond length is 2.80 Å. The Mg(2)-Si(7) bond length is 2.81 Å. Both Mg(2)-Si(2) bond lengths are 3.04 Å. Both Mg(2)-Si(3) bond lengths are 2.77 Å. Both Mg(2)-Si(8) bond lengths are 2.77 Å. In the third Mg site, Mg(3) is bonded to one Si(1), one Si(6), two equivalent Si(2), and two equivalent Si(4) atoms to form distorted edge-sharing MgSi6 octahedra. The Mg(3)-Si(1) bond length is 2.78 Å. The Mg(3)-Si(6) bond length is 3.03 Å. Both Mg(3)-Si(2) bond lengths are 2.94 Å. Both Mg(3)-Si(4) bond lengths are 2.88 Å. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one Si(3), one Si(4), one Si(8), two equivalent Si(1), and two equivalent Si(5) atoms. The Mg(4)-Si(3) bond length is 2.81 Å. The Mg(4)-Si(4) bond length is 2.84 Å. The Mg(4)-Si(8) bond length is 3.02 Å. Both Mg(4)-Si(1) bond lengths are 2.89 Å. Both Mg(4)-Si(5) bond lengths are 2.86 Å. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), two equivalent Mg(1), two equivalent Mg(4), and two equivalent Si(8) atoms. Both Si(1)-Si(8) bond lengths are 2.43 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(1), two equivalent Mg(2), two equivalent Mg(3), one Si(3), and two equivalent Si(7) atoms. The Si(2)-Si(3) bond length is 2.47 Å. Both Si(2)-Si(7) bond lengths are 2.44 Å. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to one Mg(4), two equivalent Mg(2), one Si(2), and two equivalent Si(6) atoms. Both Si(3)-Si(6) bond lengths are 2.38 Å. In the fourth Si site, Si(4) is bonded in a 6-coordinate geometry to one Mg(4), two equivalent Mg(3), one Si(8), and two equivalent Si(5) atoms. The Si(4)-Si(8) bond length is 2.40 Å. Both Si(4)-Si(5) bond lengths are 2.43 Å. In the fifth Si site, Si(5) is bonded in a 6-coordinate geometry to one Mg(2), two equivalent Mg(4), one Si(7), two equivalent Si(4), and two equivalent Si(8) atoms. The Si(5)-Si(7) bond length is 2.47 Å. Both Si(5)-Si(8) bond lengths are 2.86 Å. In the sixth Si site, Si(6) is bonded to one Mg(3), two equivalent Mg(1), one Si(7), and two equivalent Si(3) atoms to form distorted edge-sharing SiMg3Si3 octahedra. The Si(6)-Si(7) bond length is 2.46 Å. In the seventh Si site, Si(7) is bonded in a 5-coordinate geometry to one Mg(2), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the eighth Si site, Si(8) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), two equivalent Mg(2), one Si(4), two equivalent Si(1), and two equivalent Si(5) atoms.