Mg6Si5 crystallizes in the triclinic P1 space group. There are twelve inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted linear geometry to one Si(7) and one Si(9) atom. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Mg(3), two equivalent Mg(7), one Si(10), one Si(5), two equivalent Si(1), and two equivalent Si(2) atoms. In the third Mg site, Mg(3) is bonded in a 13-coordinate geometry to one Mg(2), one Mg(8), two equivalent Mg(7), one Si(1), one Si(3), one Si(7), two equivalent Si(10), two equivalent Si(2), and two equivalent Si(6) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(2), one Si(4), one Si(5), one Si(9), two equivalent Si(1), and two equivalent Si(8) atoms. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(5), two equivalent Si(8), and two equivalent Si(9) atoms. In the sixth Mg site, Mg(6) is bonded in a 5-coordinate geometry to one Si(10), one Si(6), one Si(7), and two equivalent Si(3) atoms. In the seventh Mg site, Mg(7) is bonded in a 10-coordinate geometry to one Mg(8), two equivalent Mg(2), two equivalent Mg(3), one Si(10), one Si(3), one Si(7), and two equivalent Si(6) atoms. In the eighth Mg site, Mg(8) is bonded in a 7-coordinate geometry to one Mg(3), one Mg(7), one Si(4), one Si(8), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(5) atoms. In the ninth Mg site, Mg(9) is bonded in a 1-coordinate geometry to one Si(4), one Si(8), and one Si(9) atom. In the tenth Mg site, Mg(10) is bonded in a 5-coordinate geometry to one Si(10), one Si(3), one Si(6), and two equivalent Si(7) atoms. In the eleventh Mg site, Mg(11) is bonded in a distorted single-bond geometry to one Si(3) atom. In the twelfth Mg site, Mg(12) is bonded in a 4-coordinate geometry to one Si(4), one Si(8), and two equivalent Si(9) atoms. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(3), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(8), one Si(2), one Si(4), and one Si(8) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(4), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(8), one Si(1), and one Si(6) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(10), one Mg(11), one Mg(3), one Mg(7), two equivalent Mg(6), one Si(7), and two equivalent Si(10) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(12), one Mg(4), one Mg(8), one Mg(9), one Si(1), one Si(5), one Si(8), and one Si(9) atom. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), two equivalent Mg(8), one Si(4), one Si(8), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to one Mg(10), one Mg(6), two equivalent Mg(3), two equivalent Mg(7), one Si(10), one Si(2), and two equivalent Si(7) atoms. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(6), one Mg(7), two equivalent Mg(10), one Si(3), and two equivalent Si(6) atoms. In the eighth Si site, Si(8) is bonded in a 10-coordinate geometry to one Mg(12), one Mg(8), one Mg(9), two equivalent Mg(4), two equivalent Mg(5), one Si(1), one Si(4), and one Si(5) atom. In the ninth Si site, Si(9) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(9), two equivalent Mg(12), two equivalent Mg(5), one Si(4), and one Si(5) atom. In the tenth Si site, Si(10) is bonded in a 9-coordinate geometry to one Mg(10), one Mg(2), one Mg(6), one Mg(7), two equivalent Mg(3), one Si(6), and two equivalent Si(3) atoms.
Mg6Si5 crystallizes in the triclinic P1 space group. There are twelve inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted linear geometry to one Si(7) and one Si(9) atom. The Mg(1)-Si(7) bond length is 2.79 Å. The Mg(1)-Si(9) bond length is 2.86 Å. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one Mg(3), two equivalent Mg(7), one Si(10), one Si(5), two equivalent Si(1), and two equivalent Si(2) atoms. The Mg(2)-Mg(3) bond length is 3.11 Å. There is one shorter (3.11 Å) and one longer (3.13 Å) Mg(2)-Mg(7) bond length. The Mg(2)-Si(10) bond length is 2.84 Å. The Mg(2)-Si(5) bond length is 3.02 Å. There is one shorter (2.78 Å) and one longer (3.08 Å) Mg(2)-Si(1) bond length. There is one shorter (2.80 Å) and one longer (3.26 Å) Mg(2)-Si(2) bond length. In the third Mg site, Mg(3) is bonded in a 13-coordinate geometry to one Mg(2), one Mg(8), two equivalent Mg(7), one Si(1), one Si(3), one Si(7), two equivalent Si(10), two equivalent Si(2), and two equivalent Si(6) atoms. The Mg(3)-Mg(8) bond length is 3.33 Å. There is one shorter (3.00 Å) and one longer (3.07 Å) Mg(3)-Mg(7) bond length. The Mg(3)-Si(1) bond length is 2.84 Å. The Mg(3)-Si(3) bond length is 2.83 Å. The Mg(3)-Si(7) bond length is 2.83 Å. There is one shorter (2.83 Å) and one longer (3.10 Å) Mg(3)-Si(10) bond length. There is one shorter (2.81 Å) and one longer (3.00 Å) Mg(3)-Si(2) bond length. There is one shorter (3.02 Å) and one longer (3.09 Å) Mg(3)-Si(6) bond length. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(2), one Si(4), one Si(5), one Si(9), two equivalent Si(1), and two equivalent Si(8) atoms. The Mg(4)-Si(2) bond length is 3.14 Å. The Mg(4)-Si(4) bond length is 3.10 Å. The Mg(4)-Si(5) bond length is 2.83 Å. The Mg(4)-Si(9) bond length is 2.88 Å. There is one shorter (2.75 Å) and one longer (2.86 Å) Mg(4)-Si(1) bond length. There is one shorter (2.77 Å) and one longer (2.96 Å) Mg(4)-Si(8) bond length. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(5), two equivalent Si(8), and two equivalent Si(9) atoms. The Mg(5)-Si(5) bond length is 2.75 Å. There is one shorter (2.79 Å) and one longer (2.92 Å) Mg(5)-Si(8) bond length. There is one shorter (2.92 Å) and one longer (3.12 Å) Mg(5)-Si(9) bond length. In the sixth Mg site, Mg(6) is bonded in a 5-coordinate geometry to one Si(10), one Si(6), one Si(7), and two equivalent Si(3) atoms. The Mg(6)-Si(10) bond length is 2.83 Å. The Mg(6)-Si(6) bond length is 2.93 Å. The Mg(6)-Si(7) bond length is 2.96 Å. There is one shorter (2.95 Å) and one longer (3.11 Å) Mg(6)-Si(3) bond length. In the seventh Mg site, Mg(7) is bonded in a 10-coordinate geometry to one Mg(8), two equivalent Mg(2), two equivalent Mg(3), one Si(10), one Si(3), one Si(7), and two equivalent Si(6) atoms. The Mg(7)-Mg(8) bond length is 3.16 Å. The Mg(7)-Si(10) bond length is 2.77 Å. The Mg(7)-Si(3) bond length is 2.76 Å. The Mg(7)-Si(7) bond length is 2.83 Å. There is one shorter (3.01 Å) and one longer (3.09 Å) Mg(7)-Si(6) bond length. In the eighth Mg site, Mg(8) is bonded in a 7-coordinate geometry to one Mg(3), one Mg(7), one Si(4), one Si(8), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(5) atoms. The Mg(8)-Si(4) bond length is 2.95 Å. The Mg(8)-Si(8) bond length is 2.82 Å. There is one shorter (2.95 Å) and one longer (3.14 Å) Mg(8)-Si(1) bond length. There is one shorter (2.93 Å) and one longer (3.05 Å) Mg(8)-Si(2) bond length. There is one shorter (2.96 Å) and one longer (2.98 Å) Mg(8)-Si(5) bond length. In the ninth Mg site, Mg(9) is bonded in a 1-coordinate geometry to one Si(4), one Si(8), and one Si(9) atom. The Mg(9)-Si(4) bond length is 3.11 Å. The Mg(9)-Si(8) bond length is 3.17 Å. The Mg(9)-Si(9) bond length is 2.78 Å. In the tenth Mg site, Mg(10) is bonded in a 5-coordinate geometry to one Si(10), one Si(3), one Si(6), and two equivalent Si(7) atoms. The Mg(10)-Si(10) bond length is 2.87 Å. The Mg(10)-Si(3) bond length is 2.89 Å. The Mg(10)-Si(6) bond length is 2.77 Å. There is one shorter (2.87 Å) and one longer (2.91 Å) Mg(10)-Si(7) bond length. In the eleventh Mg site, Mg(11) is bonded in a distorted single-bond geometry to one Si(3) atom. The Mg(11)-Si(3) bond length is 2.70 Å. In the twelfth Mg site, Mg(12) is bonded in a 4-coordinate geometry to one Si(4), one Si(8), and two equivalent Si(9) atoms. The Mg(12)-Si(4) bond length is 2.87 Å. The Mg(12)-Si(8) bond length is 2.91 Å. There is one shorter (2.92 Å) and one longer (2.97 Å) Mg(12)-Si(9) bond length. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Mg(3), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(8), one Si(2), one Si(4), and one Si(8) atom. The Si(1)-Si(2) bond length is 2.77 Å. The Si(1)-Si(4) bond length is 2.69 Å. The Si(1)-Si(8) bond length is 2.85 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(4), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(8), one Si(1), and one Si(6) atom. The Si(2)-Si(6) bond length is 2.51 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(10), one Mg(11), one Mg(3), one Mg(7), two equivalent Mg(6), one Si(7), and two equivalent Si(10) atoms. The Si(3)-Si(7) bond length is 2.52 Å. There is one shorter (2.65 Å) and one longer (2.86 Å) Si(3)-Si(10) bond length. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(12), one Mg(4), one Mg(8), one Mg(9), one Si(1), one Si(5), one Si(8), and one Si(9) atom. The Si(4)-Si(5) bond length is 2.58 Å. The Si(4)-Si(8) bond length is 2.76 Å. The Si(4)-Si(9) bond length is 2.60 Å. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), two equivalent Mg(8), one Si(4), one Si(8), and one Si(9) atom. The Si(5)-Si(8) bond length is 2.55 Å. The Si(5)-Si(9) bond length is 2.53 Å. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to one Mg(10), one Mg(6), two equivalent Mg(3), two equivalent Mg(7), one Si(10), one Si(2), and two equivalent Si(7) atoms. The Si(6)-Si(10) bond length is 2.54 Å. There is one shorter (2.63 Å) and one longer (2.91 Å) Si(6)-Si(7) bond length. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(6), one Mg(7), two equivalent Mg(10), one Si(3), and two equivalent Si(6) atoms. In the eighth Si site, Si(8) is bonded in a 10-coordinate geometry to one Mg(12), one Mg(8), one Mg(9), two equivalent Mg(4), two equivalent Mg(5), one Si(1), one Si(4), and one Si(5) atom. In the ninth Si site, Si(9) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(9), two equivalent Mg(12), two equivalent Mg(5), one Si(4), and one Si(5) atom. In the tenth Si site, Si(10) is bonded in a 9-coordinate geometry to one Mg(10), one Mg(2), one Mg(6), one Mg(7), two equivalent Mg(3), one Si(6), and two equivalent Si(3) atoms.