MgSi2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to two equivalent Si(3), three equivalent Si(1), three equivalent Si(2), and three equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded to two equivalent Si(2), four equivalent Si(4), and six equivalent Si(1) atoms to form a mixture of distorted edge and face-sharing MgSi12 cuboctahedra. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to two equivalent Si(2) and six equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), one Si(2), two equivalent Si(1), and two equivalent Si(4) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), three equivalent Mg(1), one Si(1), one Si(3), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), three equivalent Mg(3), one Si(2), and two equivalent Si(3) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Mg(2), three equivalent Mg(1), two equivalent Si(1), and two equivalent Si(2) atoms.
MgSi2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to two equivalent Si(3), three equivalent Si(1), three equivalent Si(2), and three equivalent Si(4) atoms. There is one shorter (2.72 Å) and one longer (3.23 Å) Mg(1)-Si(3) bond length. There is one shorter (3.14 Å) and two longer (3.25 Å) Mg(1)-Si(1) bond lengths. There is one shorter (2.83 Å) and two longer (2.89 Å) Mg(1)-Si(2) bond lengths. There is one shorter (2.78 Å) and two longer (3.12 Å) Mg(1)-Si(4) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent Si(2), four equivalent Si(4), and six equivalent Si(1) atoms to form a mixture of distorted edge and face-sharing MgSi12 cuboctahedra. Both Mg(2)-Si(2) bond lengths are 2.81 Å. All Mg(2)-Si(4) bond lengths are 2.89 Å. All Mg(2)-Si(1) bond lengths are 2.88 Å. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to two equivalent Si(2) and six equivalent Si(3) atoms. Both Mg(3)-Si(2) bond lengths are 2.91 Å. There are two shorter (2.80 Å) and four longer (2.92 Å) Mg(3)-Si(3) bond lengths. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), one Si(2), two equivalent Si(1), and two equivalent Si(4) atoms. The Si(1)-Si(2) bond length is 2.82 Å. Both Si(1)-Si(1) bond lengths are 2.59 Å. There is one shorter (2.48 Å) and one longer (2.56 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), one Mg(3), three equivalent Mg(1), one Si(1), one Si(3), and two equivalent Si(4) atoms. The Si(2)-Si(3) bond length is 2.50 Å. Both Si(2)-Si(4) bond lengths are 2.55 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent Mg(1), three equivalent Mg(3), one Si(2), and two equivalent Si(3) atoms. Both Si(3)-Si(3) bond lengths are 2.50 Å. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Mg(2), three equivalent Mg(1), two equivalent Si(1), and two equivalent Si(2) atoms.