Mg7Si4 crystallizes in the triclinic P1 space group. There are fourteen inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Mg(10), one Mg(11), one Mg(12), one Mg(4), two equivalent Mg(5), two equivalent Mg(9), one Si(6), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 2-coordinate geometry to one Si(2), one Si(3), and two equivalent Si(7) atoms. In the third Mg site, Mg(3) is bonded in a 3-coordinate geometry to one Si(3) and two equivalent Si(7) atoms. In the fourth Mg site, Mg(4) is bonded in a 3-coordinate geometry to one Mg(1), one Si(2), one Si(7), and two equivalent Si(3) atoms. In the fifth Mg site, Mg(5) is bonded in a 3-coordinate geometry to two equivalent Mg(1), one Si(2), one Si(3), and one Si(6) atom. In the sixth Mg site, Mg(6) is bonded in a 4-coordinate geometry to one Si(1), one Si(4), and two equivalent Si(8) atoms. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to one Si(5), one Si(8), and two equivalent Si(4) atoms. In the eighth Mg site, Mg(8) is bonded in a distorted single-bond geometry to one Si(3) atom. In the ninth Mg site, Mg(9) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Si(1), one Si(2), one Si(5), and one Si(6) atom. In the tenth Mg site, Mg(10) is bonded in a 3-coordinate geometry to one Mg(1), one Si(1), one Si(2), and one Si(5) atom. In the eleventh Mg site, Mg(11) is bonded in a 4-coordinate geometry to one Mg(1), one Si(5), one Si(8), and two equivalent Si(1) atoms. In the twelfth Mg site, Mg(12) is bonded in a 4-coordinate geometry to one Mg(1), one Si(1), one Si(4), and two equivalent Si(5) atoms. In the thirteenth Mg site, Mg(13) is bonded in a 3-coordinate geometry to one Si(4), one Si(7), and one Si(8) atom. In the fourteenth Mg site, Mg(14) is bonded in a 3-coordinate geometry to one Si(4), one Si(7), and one Si(8) atom. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(12), one Mg(6), one Mg(9), two equivalent Mg(11), one Si(5), and one Si(8) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(2), one Mg(4), one Mg(5), one Mg(9), two equivalent Mg(1), and one Si(6) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(8), two equivalent Mg(4), one Si(6), and one Si(7) atom. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(12), one Mg(13), one Mg(14), one Mg(6), two equivalent Mg(7), one Si(5), and one Si(8) atom. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(11), one Mg(7), one Mg(9), two equivalent Mg(12), one Si(1), and one Si(4) atom. In the sixth Si site, Si(6) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(5), one Mg(9), one Si(2), one Si(3), and one Si(7) atom. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(13), one Mg(14), one Mg(4), two equivalent Mg(2), two equivalent Mg(3), one Si(3), and one Si(6) atom. In the eighth Si site, Si(8) is bonded in a 8-coordinate geometry to one Mg(11), one Mg(13), one Mg(14), one Mg(7), two equivalent Mg(6), one Si(1), and one Si(4) atom.
Mg7Si4 crystallizes in the triclinic P1 space group. There are fourteen inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Mg(10), one Mg(11), one Mg(12), one Mg(4), two equivalent Mg(5), two equivalent Mg(9), one Si(6), and two equivalent Si(2) atoms. The Mg(1)-Mg(10) bond length is 3.06 Å. The Mg(1)-Mg(11) bond length is 3.15 Å. The Mg(1)-Mg(12) bond length is 3.18 Å. The Mg(1)-Mg(4) bond length is 3.01 Å. There is one shorter (3.09 Å) and one longer (3.11 Å) Mg(1)-Mg(5) bond length. There is one shorter (3.02 Å) and one longer (3.03 Å) Mg(1)-Mg(9) bond length. The Mg(1)-Si(6) bond length is 3.13 Å. There is one shorter (2.77 Å) and one longer (3.10 Å) Mg(1)-Si(2) bond length. In the second Mg site, Mg(2) is bonded in a 2-coordinate geometry to one Si(2), one Si(3), and two equivalent Si(7) atoms. The Mg(2)-Si(2) bond length is 2.79 Å. The Mg(2)-Si(3) bond length is 2.70 Å. There is one shorter (3.02 Å) and one longer (3.20 Å) Mg(2)-Si(7) bond length. In the third Mg site, Mg(3) is bonded in a 3-coordinate geometry to one Si(3) and two equivalent Si(7) atoms. The Mg(3)-Si(3) bond length is 3.01 Å. There is one shorter (3.01 Å) and one longer (3.03 Å) Mg(3)-Si(7) bond length. In the fourth Mg site, Mg(4) is bonded in a 3-coordinate geometry to one Mg(1), one Si(2), one Si(7), and two equivalent Si(3) atoms. The Mg(4)-Si(2) bond length is 2.62 Å. The Mg(4)-Si(7) bond length is 2.73 Å. There is one shorter (2.93 Å) and one longer (3.19 Å) Mg(4)-Si(3) bond length. In the fifth Mg site, Mg(5) is bonded in a 3-coordinate geometry to two equivalent Mg(1), one Si(2), one Si(3), and one Si(6) atom. The Mg(5)-Si(2) bond length is 2.88 Å. The Mg(5)-Si(3) bond length is 2.77 Å. The Mg(5)-Si(6) bond length is 2.98 Å. In the sixth Mg site, Mg(6) is bonded in a 4-coordinate geometry to one Si(1), one Si(4), and two equivalent Si(8) atoms. The Mg(6)-Si(1) bond length is 2.83 Å. The Mg(6)-Si(4) bond length is 2.87 Å. There is one shorter (2.90 Å) and one longer (3.07 Å) Mg(6)-Si(8) bond length. In the seventh Mg site, Mg(7) is bonded in a 4-coordinate geometry to one Si(5), one Si(8), and two equivalent Si(4) atoms. The Mg(7)-Si(5) bond length is 2.81 Å. The Mg(7)-Si(8) bond length is 2.84 Å. There is one shorter (2.81 Å) and one longer (2.86 Å) Mg(7)-Si(4) bond length. In the eighth Mg site, Mg(8) is bonded in a distorted single-bond geometry to one Si(3) atom. The Mg(8)-Si(3) bond length is 2.77 Å. In the ninth Mg site, Mg(9) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Si(1), one Si(2), one Si(5), and one Si(6) atom. The Mg(9)-Si(1) bond length is 2.77 Å. The Mg(9)-Si(2) bond length is 2.74 Å. The Mg(9)-Si(5) bond length is 2.76 Å. The Mg(9)-Si(6) bond length is 2.87 Å. In the tenth Mg site, Mg(10) is bonded in a 3-coordinate geometry to one Mg(1), one Si(1), one Si(2), and one Si(5) atom. The Mg(10)-Si(1) bond length is 2.80 Å. The Mg(10)-Si(2) bond length is 2.77 Å. The Mg(10)-Si(5) bond length is 2.82 Å. In the eleventh Mg site, Mg(11) is bonded in a 4-coordinate geometry to one Mg(1), one Si(5), one Si(8), and two equivalent Si(1) atoms. The Mg(11)-Si(5) bond length is 2.88 Å. The Mg(11)-Si(8) bond length is 2.89 Å. There is one shorter (2.79 Å) and one longer (2.88 Å) Mg(11)-Si(1) bond length. In the twelfth Mg site, Mg(12) is bonded in a 4-coordinate geometry to one Mg(1), one Si(1), one Si(4), and two equivalent Si(5) atoms. The Mg(12)-Si(1) bond length is 2.97 Å. The Mg(12)-Si(4) bond length is 2.80 Å. There is one shorter (2.86 Å) and one longer (3.02 Å) Mg(12)-Si(5) bond length. In the thirteenth Mg site, Mg(13) is bonded in a 3-coordinate geometry to one Si(4), one Si(7), and one Si(8) atom. The Mg(13)-Si(4) bond length is 2.79 Å. The Mg(13)-Si(7) bond length is 2.87 Å. The Mg(13)-Si(8) bond length is 2.95 Å. In the fourteenth Mg site, Mg(14) is bonded in a 3-coordinate geometry to one Si(4), one Si(7), and one Si(8) atom. The Mg(14)-Si(4) bond length is 2.92 Å. The Mg(14)-Si(7) bond length is 2.97 Å. The Mg(14)-Si(8) bond length is 2.72 Å. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(12), one Mg(6), one Mg(9), two equivalent Mg(11), one Si(5), and one Si(8) atom. The Si(1)-Si(5) bond length is 2.55 Å. The Si(1)-Si(8) bond length is 2.47 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(2), one Mg(4), one Mg(5), one Mg(9), two equivalent Mg(1), and one Si(6) atom. The Si(2)-Si(6) bond length is 2.50 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(8), two equivalent Mg(4), one Si(6), and one Si(7) atom. The Si(3)-Si(6) bond length is 2.44 Å. The Si(3)-Si(7) bond length is 2.52 Å. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(12), one Mg(13), one Mg(14), one Mg(6), two equivalent Mg(7), one Si(5), and one Si(8) atom. The Si(4)-Si(5) bond length is 2.51 Å. The Si(4)-Si(8) bond length is 2.55 Å. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(11), one Mg(7), one Mg(9), two equivalent Mg(12), one Si(1), and one Si(4) atom. In the sixth Si site, Si(6) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(5), one Mg(9), one Si(2), one Si(3), and one Si(7) atom. The Si(6)-Si(7) bond length is 2.56 Å. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(13), one Mg(14), one Mg(4), two equivalent Mg(2), two equivalent Mg(3), one Si(3), and one Si(6) atom. In the eighth Si site, Si(8) is bonded in a 8-coordinate geometry to one Mg(11), one Mg(13), one Mg(14), one Mg(7), two equivalent Mg(6), one Si(1), and one Si(4) atom.