Mg5Si9 is delta Molybdenum Boride-like structured and crystallizes in the triclinic P1 space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 7-coordinate geometry to one Si(11), one Si(12), one Si(14), one Si(17), one Si(4), one Si(6), and one Si(8) atom. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one Si(10), one Si(13), one Si(17), one Si(18), one Si(3), and one Si(7) atom. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(14), one Si(17), one Si(18), one Si(3), one Si(6), and one Si(7) atom. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one Si(13), one Si(16), one Si(17), one Si(18), one Si(3), one Si(5), and one Si(9) atom. In the fifth Mg site, Mg(5) is bonded in a 6-coordinate geometry to one Si(10), one Si(14), one Si(17), one Si(3), one Si(6), and one Si(7) atom. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Si(10), one Si(13), one Si(17), one Si(18), one Si(3), and one Si(8) atom. In the seventh Mg site, Mg(7) is bonded in a 7-coordinate geometry to one Si(1), one Si(12), one Si(15), one Si(16), one Si(18), one Si(3), one Si(5), one Si(7), and one Si(9) atom. In the eighth Mg site, Mg(8) is bonded in a 9-coordinate geometry to one Si(1), one Si(10), one Si(12), one Si(15), one Si(16), one Si(2), one Si(4), one Si(6), and one Si(8) atom. In the ninth Mg site, Mg(9) is bonded in a 8-coordinate geometry to one Si(1), one Si(11), one Si(12), one Si(13), one Si(15), one Si(16), one Si(5), one Si(7), and one Si(9) atom. In the tenth Mg site, Mg(10) is bonded in a 9-coordinate geometry to one Si(11), one Si(12), one Si(15), one Si(16), one Si(2), one Si(4), one Si(5), one Si(6), and one Si(8) atom. There are eighteen inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(7), one Mg(8), one Mg(9), one Si(12), one Si(13), one Si(16), and one Si(5) atom. In the second Si site, Si(2) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(8), one Si(11), one Si(14), one Si(15), one Si(16), and one Si(4) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), one Si(13), one Si(7), and one Si(9) atom. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(10), one Mg(8), one Si(10), one Si(12), one Si(14), one Si(17), and one Si(2) atom. In the fifth Si site, Si(5) is bonded in a 10-coordinate geometry to one Mg(10), one Mg(4), one Mg(7), one Mg(9), one Si(1), one Si(15), one Si(16), one Si(18), one Si(7), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(10), one Mg(3), one Mg(5), one Mg(8), one Si(10), one Si(11), one Si(14), one Si(15), and one Si(17) atom. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(7), one Mg(9), one Si(13), one Si(18), one Si(3), and one Si(5) atom. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(10), one Mg(6), one Mg(8), one Si(10), one Si(14), and one Si(17) atom. In the ninth Si site, Si(9) is bonded in a 7-coordinate geometry to one Mg(4), one Mg(7), one Mg(9), one Si(15), one Si(16), one Si(3), and one Si(5) atom. In the tenth Si site, Si(10) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(5), one Mg(6), one Mg(8), one Si(4), one Si(6), and one Si(8) atom. In the eleventh Si site, Si(11) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(10), one Mg(9), one Si(12), one Si(14), one Si(2), and one Si(6) atom. In the twelfth Si site, Si(12) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(10), one Mg(7), one Mg(8), one Mg(9), one Si(1), one Si(11), one Si(15), and one Si(4) atom. In the thirteenth Si site, Si(13) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(6), one Mg(9), one Si(1), one Si(3), and one Si(7) atom. In the fourteenth Si site, Si(14) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Si(11), one Si(2), one Si(4), one Si(6), and one Si(8) atom. In the fifteenth Si site, Si(15) is bonded in a 7-coordinate geometry to one Mg(10), one Mg(7), one Mg(8), one Mg(9), one Si(12), one Si(2), one Si(5), one Si(6), and one Si(9) atom. In the sixteenth Si site, Si(16) is bonded in a 1-coordinate geometry to one Mg(10), one Mg(4), one Mg(7), one Mg(8), one Mg(9), one Si(1), one Si(2), one Si(5), and one Si(9) atom. In the seventeenth Si site, Si(17) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Si(4), one Si(6), and one Si(8) atom. In the eighteenth Si site, Si(18) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Mg(7), one Si(5), and one Si(7) atom.
Mg5Si9 is delta Molybdenum Boride-like structured and crystallizes in the triclinic P1 space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 7-coordinate geometry to one Si(11), one Si(12), one Si(14), one Si(17), one Si(4), one Si(6), and one Si(8) atom. The Mg(1)-Si(11) bond length is 2.98 Å. The Mg(1)-Si(12) bond length is 2.77 Å. The Mg(1)-Si(14) bond length is 2.80 Å. The Mg(1)-Si(17) bond length is 2.96 Å. The Mg(1)-Si(4) bond length is 2.91 Å. The Mg(1)-Si(6) bond length is 2.95 Å. The Mg(1)-Si(8) bond length is 2.89 Å. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one Si(10), one Si(13), one Si(17), one Si(18), one Si(3), and one Si(7) atom. The Mg(2)-Si(10) bond length is 2.92 Å. The Mg(2)-Si(13) bond length is 2.92 Å. The Mg(2)-Si(17) bond length is 2.81 Å. The Mg(2)-Si(18) bond length is 3.01 Å. The Mg(2)-Si(3) bond length is 2.91 Å. The Mg(2)-Si(7) bond length is 2.86 Å. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(14), one Si(17), one Si(18), one Si(3), one Si(6), and one Si(7) atom. The Mg(3)-Si(14) bond length is 2.77 Å. The Mg(3)-Si(17) bond length is 2.99 Å. The Mg(3)-Si(18) bond length is 2.83 Å. The Mg(3)-Si(3) bond length is 2.76 Å. The Mg(3)-Si(6) bond length is 3.23 Å. The Mg(3)-Si(7) bond length is 2.87 Å. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one Si(13), one Si(16), one Si(17), one Si(18), one Si(3), one Si(5), and one Si(9) atom. The Mg(4)-Si(13) bond length is 2.82 Å. The Mg(4)-Si(16) bond length is 2.85 Å. The Mg(4)-Si(17) bond length is 3.13 Å. The Mg(4)-Si(18) bond length is 3.02 Å. The Mg(4)-Si(3) bond length is 3.04 Å. The Mg(4)-Si(5) bond length is 3.03 Å. The Mg(4)-Si(9) bond length is 2.71 Å. In the fifth Mg site, Mg(5) is bonded in a 6-coordinate geometry to one Si(10), one Si(14), one Si(17), one Si(3), one Si(6), and one Si(7) atom. The Mg(5)-Si(10) bond length is 3.00 Å. The Mg(5)-Si(14) bond length is 2.73 Å. The Mg(5)-Si(17) bond length is 2.81 Å. The Mg(5)-Si(3) bond length is 2.85 Å. The Mg(5)-Si(6) bond length is 3.01 Å. The Mg(5)-Si(7) bond length is 2.92 Å. In the sixth Mg site, Mg(6) is bonded in a 6-coordinate geometry to one Si(10), one Si(13), one Si(17), one Si(18), one Si(3), and one Si(8) atom. The Mg(6)-Si(10) bond length is 2.82 Å. The Mg(6)-Si(13) bond length is 2.74 Å. The Mg(6)-Si(17) bond length is 2.90 Å. The Mg(6)-Si(18) bond length is 2.79 Å. The Mg(6)-Si(3) bond length is 2.78 Å. The Mg(6)-Si(8) bond length is 2.76 Å. In the seventh Mg site, Mg(7) is bonded in a 7-coordinate geometry to one Si(1), one Si(12), one Si(15), one Si(16), one Si(18), one Si(3), one Si(5), one Si(7), and one Si(9) atom. The Mg(7)-Si(1) bond length is 3.05 Å. The Mg(7)-Si(12) bond length is 2.95 Å. The Mg(7)-Si(15) bond length is 2.95 Å. The Mg(7)-Si(16) bond length is 2.67 Å. The Mg(7)-Si(18) bond length is 3.10 Å. The Mg(7)-Si(3) bond length is 2.75 Å. The Mg(7)-Si(5) bond length is 3.16 Å. The Mg(7)-Si(7) bond length is 3.21 Å. The Mg(7)-Si(9) bond length is 2.88 Å. In the eighth Mg site, Mg(8) is bonded in a 9-coordinate geometry to one Si(1), one Si(10), one Si(12), one Si(15), one Si(16), one Si(2), one Si(4), one Si(6), and one Si(8) atom. The Mg(8)-Si(1) bond length is 2.98 Å. The Mg(8)-Si(10) bond length is 2.84 Å. The Mg(8)-Si(12) bond length is 2.99 Å. The Mg(8)-Si(15) bond length is 2.78 Å. The Mg(8)-Si(16) bond length is 3.14 Å. The Mg(8)-Si(2) bond length is 2.88 Å. The Mg(8)-Si(4) bond length is 3.02 Å. The Mg(8)-Si(6) bond length is 3.11 Å. The Mg(8)-Si(8) bond length is 2.84 Å. In the ninth Mg site, Mg(9) is bonded in a 8-coordinate geometry to one Si(1), one Si(11), one Si(12), one Si(13), one Si(15), one Si(16), one Si(5), one Si(7), and one Si(9) atom. The Mg(9)-Si(1) bond length is 2.82 Å. The Mg(9)-Si(11) bond length is 2.85 Å. The Mg(9)-Si(12) bond length is 3.15 Å. The Mg(9)-Si(13) bond length is 2.83 Å. The Mg(9)-Si(15) bond length is 2.88 Å. The Mg(9)-Si(16) bond length is 2.99 Å. The Mg(9)-Si(5) bond length is 2.86 Å. The Mg(9)-Si(7) bond length is 2.86 Å. The Mg(9)-Si(9) bond length is 2.85 Å. In the tenth Mg site, Mg(10) is bonded in a 9-coordinate geometry to one Si(11), one Si(12), one Si(15), one Si(16), one Si(2), one Si(4), one Si(5), one Si(6), and one Si(8) atom. The Mg(10)-Si(11) bond length is 2.96 Å. The Mg(10)-Si(12) bond length is 2.86 Å. The Mg(10)-Si(15) bond length is 2.99 Å. The Mg(10)-Si(16) bond length is 2.90 Å. The Mg(10)-Si(2) bond length is 2.99 Å. The Mg(10)-Si(4) bond length is 2.81 Å. The Mg(10)-Si(5) bond length is 2.81 Å. The Mg(10)-Si(6) bond length is 2.94 Å. The Mg(10)-Si(8) bond length is 2.87 Å. There are eighteen inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(7), one Mg(8), one Mg(9), one Si(12), one Si(13), one Si(16), and one Si(5) atom. The Si(1)-Si(12) bond length is 2.54 Å. The Si(1)-Si(13) bond length is 2.50 Å. The Si(1)-Si(16) bond length is 2.56 Å. The Si(1)-Si(5) bond length is 2.56 Å. In the second Si site, Si(2) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(8), one Si(11), one Si(14), one Si(15), one Si(16), and one Si(4) atom. The Si(2)-Si(11) bond length is 2.51 Å. The Si(2)-Si(14) bond length is 2.79 Å. The Si(2)-Si(15) bond length is 2.44 Å. The Si(2)-Si(16) bond length is 2.45 Å. The Si(2)-Si(4) bond length is 2.47 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Mg(7), one Si(13), one Si(7), and one Si(9) atom. The Si(3)-Si(13) bond length is 2.60 Å. The Si(3)-Si(7) bond length is 2.58 Å. The Si(3)-Si(9) bond length is 2.40 Å. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(10), one Mg(8), one Si(10), one Si(12), one Si(14), one Si(17), and one Si(2) atom. The Si(4)-Si(10) bond length is 2.51 Å. The Si(4)-Si(12) bond length is 2.74 Å. The Si(4)-Si(14) bond length is 2.52 Å. The Si(4)-Si(17) bond length is 2.56 Å. In the fifth Si site, Si(5) is bonded in a 10-coordinate geometry to one Mg(10), one Mg(4), one Mg(7), one Mg(9), one Si(1), one Si(15), one Si(16), one Si(18), one Si(7), and one Si(9) atom. The Si(5)-Si(15) bond length is 2.91 Å. The Si(5)-Si(16) bond length is 2.90 Å. The Si(5)-Si(18) bond length is 2.47 Å. The Si(5)-Si(7) bond length is 2.58 Å. The Si(5)-Si(9) bond length is 2.51 Å. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to one Mg(1), one Mg(10), one Mg(3), one Mg(5), one Mg(8), one Si(10), one Si(11), one Si(14), one Si(15), and one Si(17) atom. The Si(6)-Si(10) bond length is 2.55 Å. The Si(6)-Si(11) bond length is 2.56 Å. The Si(6)-Si(14) bond length is 2.79 Å. The Si(6)-Si(15) bond length is 2.95 Å. The Si(6)-Si(17) bond length is 2.65 Å. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), one Mg(5), one Mg(7), one Mg(9), one Si(13), one Si(18), one Si(3), and one Si(5) atom. The Si(7)-Si(13) bond length is 2.41 Å. The Si(7)-Si(18) bond length is 2.50 Å. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(10), one Mg(6), one Mg(8), one Si(10), one Si(14), and one Si(17) atom. The Si(8)-Si(10) bond length is 2.49 Å. The Si(8)-Si(14) bond length is 2.46 Å. The Si(8)-Si(17) bond length is 2.44 Å. In the ninth Si site, Si(9) is bonded in a 7-coordinate geometry to one Mg(4), one Mg(7), one Mg(9), one Si(15), one Si(16), one Si(3), and one Si(5) atom. The Si(9)-Si(15) bond length is 2.45 Å. The Si(9)-Si(16) bond length is 2.44 Å. In the tenth Si site, Si(10) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(5), one Mg(6), one Mg(8), one Si(4), one Si(6), and one Si(8) atom. In the eleventh Si site, Si(11) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(10), one Mg(9), one Si(12), one Si(14), one Si(2), and one Si(6) atom. The Si(11)-Si(12) bond length is 2.49 Å. The Si(11)-Si(14) bond length is 2.46 Å. In the twelfth Si site, Si(12) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(10), one Mg(7), one Mg(8), one Mg(9), one Si(1), one Si(11), one Si(15), and one Si(4) atom. The Si(12)-Si(15) bond length is 2.57 Å. In the thirteenth Si site, Si(13) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(6), one Mg(9), one Si(1), one Si(3), and one Si(7) atom. In the fourteenth Si site, Si(14) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(5), one Si(11), one Si(2), one Si(4), one Si(6), and one Si(8) atom. In the fifteenth Si site, Si(15) is bonded in a 7-coordinate geometry to one Mg(10), one Mg(7), one Mg(8), one Mg(9), one Si(12), one Si(2), one Si(5), one Si(6), and one Si(9) atom. In the sixteenth Si site, Si(16) is bonded in a 1-coordinate geometry to one Mg(10), one Mg(4), one Mg(7), one Mg(8), one Mg(9), one Si(1), one Si(2), one Si(5), and one Si(9) atom. In the seventeenth Si site, Si(17) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one Mg(4), one Mg(5), one Mg(6), one Si(4), one Si(6), and one Si(8) atom. In the eighteenth Si site, Si(18) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(6), one Mg(7), one Si(5), and one Si(7) atom.