Mg4Si3 crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Mg(4), one Mg(7), one Mg(8), one Si(2), one Si(3), one Si(4), one Si(5), and one Si(6) atom. In the second Mg site, Mg(2) is bonded in a 3-coordinate geometry to one Mg(4), two equivalent Mg(8), one Si(3), one Si(5), and one Si(6) atom. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Mg(4), one Mg(7), one Si(2), one Si(3), one Si(4), one Si(5), and two equivalent Si(1) atoms. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(8), two equivalent Mg(5), two equivalent Mg(6), one Si(1), one Si(2), one Si(4), and one Si(5) atom. In the fifth Mg site, Mg(5) is bonded in a 2-coordinate geometry to one Mg(7), one Mg(8), two equivalent Mg(4), one Si(3), one Si(4), and one Si(6) atom. In the sixth Mg site, Mg(6) is bonded in a 5-coordinate geometry to one Mg(7), one Mg(8), two equivalent Mg(4), one Si(1), one Si(2), one Si(3), one Si(5), and one Si(6) atom. In the seventh Mg site, Mg(7) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Mg(6), one Mg(8), one Si(1), one Si(3), one Si(6), two equivalent Si(4), and two equivalent Si(5) atoms. In the eighth Mg site, Mg(8) is bonded in a 13-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(6), one Mg(7), two equivalent Mg(2), one Si(1), one Si(2), one Si(3), one Si(6), and two equivalent Si(4) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(4), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(3), one Si(2), one Si(3), one Si(4), and one Si(6) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(6), one Mg(8), one Si(1), one Si(5), and one Si(6) atom. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), one Mg(8), and one Si(1) atom. In the fourth Si site, Si(4) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(5), two equivalent Mg(7), two equivalent Mg(8), one Si(1), and one Si(5) atom. In the fifth Si site, Si(5) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), two equivalent Mg(7), one Si(2), one Si(4), and one Si(6) atom. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(5), one Mg(6), one Mg(7), one Mg(8), one Si(1), one Si(2), and one Si(5) atom.
Mg4Si3 crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Mg(4), one Mg(7), one Mg(8), one Si(2), one Si(3), one Si(4), one Si(5), and one Si(6) atom. The Mg(1)-Mg(4) bond length is 3.16 Å. The Mg(1)-Mg(7) bond length is 2.99 Å. The Mg(1)-Mg(8) bond length is 3.27 Å. The Mg(1)-Si(2) bond length is 2.72 Å. The Mg(1)-Si(3) bond length is 2.73 Å. The Mg(1)-Si(4) bond length is 2.82 Å. The Mg(1)-Si(5) bond length is 2.91 Å. The Mg(1)-Si(6) bond length is 3.04 Å. In the second Mg site, Mg(2) is bonded in a 3-coordinate geometry to one Mg(4), two equivalent Mg(8), one Si(3), one Si(5), and one Si(6) atom. The Mg(2)-Mg(4) bond length is 3.00 Å. There is one shorter (3.07 Å) and one longer (3.16 Å) Mg(2)-Mg(8) bond length. The Mg(2)-Si(3) bond length is 2.87 Å. The Mg(2)-Si(5) bond length is 3.04 Å. The Mg(2)-Si(6) bond length is 2.80 Å. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Mg(4), one Mg(7), one Si(2), one Si(3), one Si(4), one Si(5), and two equivalent Si(1) atoms. The Mg(3)-Mg(4) bond length is 3.06 Å. The Mg(3)-Mg(7) bond length is 2.93 Å. The Mg(3)-Si(2) bond length is 2.99 Å. The Mg(3)-Si(3) bond length is 2.84 Å. The Mg(3)-Si(4) bond length is 2.78 Å. The Mg(3)-Si(5) bond length is 2.90 Å. There is one shorter (2.79 Å) and one longer (3.19 Å) Mg(3)-Si(1) bond length. In the fourth Mg site, Mg(4) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(8), two equivalent Mg(5), two equivalent Mg(6), one Si(1), one Si(2), one Si(4), and one Si(5) atom. The Mg(4)-Mg(8) bond length is 3.18 Å. There is one shorter (3.03 Å) and one longer (3.23 Å) Mg(4)-Mg(5) bond length. There is one shorter (2.96 Å) and one longer (3.13 Å) Mg(4)-Mg(6) bond length. The Mg(4)-Si(1) bond length is 2.87 Å. The Mg(4)-Si(2) bond length is 2.90 Å. The Mg(4)-Si(4) bond length is 2.99 Å. The Mg(4)-Si(5) bond length is 3.15 Å. In the fifth Mg site, Mg(5) is bonded in a 2-coordinate geometry to one Mg(7), one Mg(8), two equivalent Mg(4), one Si(3), one Si(4), and one Si(6) atom. The Mg(5)-Mg(7) bond length is 3.00 Å. The Mg(5)-Mg(8) bond length is 3.27 Å. The Mg(5)-Si(3) bond length is 2.91 Å. The Mg(5)-Si(4) bond length is 2.88 Å. The Mg(5)-Si(6) bond length is 3.18 Å. In the sixth Mg site, Mg(6) is bonded in a 5-coordinate geometry to one Mg(7), one Mg(8), two equivalent Mg(4), one Si(1), one Si(2), one Si(3), one Si(5), and one Si(6) atom. The Mg(6)-Mg(7) bond length is 3.14 Å. The Mg(6)-Mg(8) bond length is 3.08 Å. The Mg(6)-Si(1) bond length is 3.01 Å. The Mg(6)-Si(2) bond length is 2.78 Å. The Mg(6)-Si(3) bond length is 2.92 Å. The Mg(6)-Si(5) bond length is 2.81 Å. The Mg(6)-Si(6) bond length is 2.74 Å. In the seventh Mg site, Mg(7) is bonded in a 12-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Mg(6), one Mg(8), one Si(1), one Si(3), one Si(6), two equivalent Si(4), and two equivalent Si(5) atoms. The Mg(7)-Mg(8) bond length is 3.10 Å. The Mg(7)-Si(1) bond length is 2.92 Å. The Mg(7)-Si(3) bond length is 2.75 Å. The Mg(7)-Si(6) bond length is 2.86 Å. There is one shorter (2.93 Å) and one longer (3.02 Å) Mg(7)-Si(4) bond length. There is one shorter (2.94 Å) and one longer (3.13 Å) Mg(7)-Si(5) bond length. In the eighth Mg site, Mg(8) is bonded in a 13-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(6), one Mg(7), two equivalent Mg(2), one Si(1), one Si(2), one Si(3), one Si(6), and two equivalent Si(4) atoms. The Mg(8)-Si(1) bond length is 2.81 Å. The Mg(8)-Si(2) bond length is 2.80 Å. The Mg(8)-Si(3) bond length is 3.33 Å. The Mg(8)-Si(6) bond length is 3.00 Å. There is one shorter (3.14 Å) and one longer (3.22 Å) Mg(8)-Si(4) bond length. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(4), one Mg(6), one Mg(7), one Mg(8), two equivalent Mg(3), one Si(2), one Si(3), one Si(4), and one Si(6) atom. The Si(1)-Si(2) bond length is 2.67 Å. The Si(1)-Si(3) bond length is 2.87 Å. The Si(1)-Si(4) bond length is 2.94 Å. The Si(1)-Si(6) bond length is 2.55 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(6), one Mg(8), one Si(1), one Si(5), and one Si(6) atom. The Si(2)-Si(5) bond length is 2.47 Å. The Si(2)-Si(6) bond length is 2.55 Å. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(5), one Mg(6), one Mg(7), one Mg(8), and one Si(1) atom. In the fourth Si site, Si(4) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(3), one Mg(4), one Mg(5), two equivalent Mg(7), two equivalent Mg(8), one Si(1), and one Si(5) atom. The Si(4)-Si(5) bond length is 2.85 Å. In the fifth Si site, Si(5) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(6), two equivalent Mg(7), one Si(2), one Si(4), and one Si(6) atom. The Si(5)-Si(6) bond length is 2.66 Å. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(5), one Mg(6), one Mg(7), one Mg(8), one Si(1), one Si(2), and one Si(5) atom.