MgSi2 crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 14-coordinate geometry to two equivalent Mg(1), two equivalent Si(1), two equivalent Si(5), four equivalent Si(3), and four equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded to two equivalent Mg(2), two equivalent Mg(3), two equivalent Si(2), two equivalent Si(6), and four equivalent Si(4) atoms to form a mixture of distorted corner and face-sharing MgMg4Si8 cuboctahedra. In the third Mg site, Mg(3) is bonded in a 13-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Si(1), two equivalent Si(2), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(5) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to two equivalent Mg(1), four equivalent Mg(3), one Si(5), two equivalent Si(1), and two equivalent Si(4) atoms. In the second Si site, Si(2) is bonded in a 11-coordinate geometry to two equivalent Mg(2), four equivalent Mg(3), one Si(6), two equivalent Si(2), and two equivalent Si(3) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(3), one Si(2), one Si(4), one Si(5), one Si(6), and two equivalent Si(3) atoms. In the fourth Si site, Si(4) is bonded in a 11-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), one Si(1), one Si(3), one Si(6), and two equivalent Si(4) atoms. In the fifth Si site, Si(5) is bonded in a 11-coordinate geometry to two equivalent Mg(1), four equivalent Mg(3), one Si(1), two equivalent Si(3), and two equivalent Si(5) atoms. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to two equivalent Mg(2), one Si(2), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(6) atoms.
MgSi2 crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 14-coordinate geometry to two equivalent Mg(1), two equivalent Si(1), two equivalent Si(5), four equivalent Si(3), and four equivalent Si(4) atoms. Both Mg(1)-Mg(1) bond lengths are 2.78 Å. Both Mg(1)-Si(1) bond lengths are 2.93 Å. Both Mg(1)-Si(5) bond lengths are 2.88 Å. All Mg(1)-Si(3) bond lengths are 2.95 Å. All Mg(1)-Si(4) bond lengths are 2.93 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(2), two equivalent Mg(3), two equivalent Si(2), two equivalent Si(6), and four equivalent Si(4) atoms to form a mixture of distorted corner and face-sharing MgMg4Si8 cuboctahedra. Both Mg(2)-Mg(2) bond lengths are 2.78 Å. Both Mg(2)-Mg(3) bond lengths are 3.00 Å. Both Mg(2)-Si(2) bond lengths are 2.98 Å. Both Mg(2)-Si(6) bond lengths are 2.83 Å. All Mg(2)-Si(4) bond lengths are 2.89 Å. In the third Mg site, Mg(3) is bonded in a 13-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Si(1), two equivalent Si(2), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(5) atoms. Both Mg(3)-Mg(3) bond lengths are 2.78 Å. Both Mg(3)-Si(1) bond lengths are 2.92 Å. Both Mg(3)-Si(2) bond lengths are 2.93 Å. Both Mg(3)-Si(3) bond lengths are 2.88 Å. Both Mg(3)-Si(4) bond lengths are 2.96 Å. Both Mg(3)-Si(5) bond lengths are 2.85 Å. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to two equivalent Mg(1), four equivalent Mg(3), one Si(5), two equivalent Si(1), and two equivalent Si(4) atoms. The Si(1)-Si(5) bond length is 2.63 Å. Both Si(1)-Si(1) bond lengths are 2.78 Å. Both Si(1)-Si(4) bond lengths are 2.51 Å. In the second Si site, Si(2) is bonded in a 11-coordinate geometry to two equivalent Mg(2), four equivalent Mg(3), one Si(6), two equivalent Si(2), and two equivalent Si(3) atoms. The Si(2)-Si(6) bond length is 2.63 Å. Both Si(2)-Si(2) bond lengths are 2.78 Å. Both Si(2)-Si(3) bond lengths are 2.82 Å. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(3), one Si(2), one Si(4), one Si(5), one Si(6), and two equivalent Si(3) atoms. The Si(3)-Si(4) bond length is 2.60 Å. The Si(3)-Si(5) bond length is 2.63 Å. The Si(3)-Si(6) bond length is 2.50 Å. Both Si(3)-Si(3) bond lengths are 2.78 Å. In the fourth Si site, Si(4) is bonded in a 11-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), one Si(1), one Si(3), one Si(6), and two equivalent Si(4) atoms. The Si(4)-Si(6) bond length is 2.88 Å. Both Si(4)-Si(4) bond lengths are 2.78 Å. In the fifth Si site, Si(5) is bonded in a 11-coordinate geometry to two equivalent Mg(1), four equivalent Mg(3), one Si(1), two equivalent Si(3), and two equivalent Si(5) atoms. Both Si(5)-Si(5) bond lengths are 2.78 Å. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to two equivalent Mg(2), one Si(2), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(6) atoms. Both Si(6)-Si(6) bond lengths are 2.78 Å.