Mg5Si6 crystallizes in the monoclinic Pm space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 2-coordinate geometry to one Si(1) and one Si(2) atom. In the second Mg site, Mg(2) is bonded in a square co-planar geometry to one Si(3), one Si(4), one Si(7), and one Si(8) atom. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(5), two equivalent Si(4), two equivalent Si(8), and two equivalent Si(9) atoms. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Si(6), two equivalent Si(10), two equivalent Si(3), and two equivalent Si(7) atoms. In the fifth Mg site, Mg(5) is bonded in a 7-coordinate geometry to one Si(6), two equivalent Si(1), two equivalent Si(10), and two equivalent Si(2) atoms. In the sixth Mg site, Mg(6) is bonded in a 7-coordinate geometry to one Si(5), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(9) atoms. In the seventh Mg site, Mg(7) is bonded in a 8-coordinate geometry to two equivalent Si(12), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(8) atoms. In the eighth Mg site, Mg(8) is bonded in a 8-coordinate geometry to two equivalent Si(11), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(7) atoms. In the ninth Mg site, Mg(9) is bonded in a 9-coordinate geometry to one Si(6), two equivalent Si(1), two equivalent Si(10), two equivalent Si(11), and two equivalent Si(7) atoms. In the tenth Mg site, Mg(10) is bonded in a 9-coordinate geometry to one Si(5), two equivalent Si(12), two equivalent Si(2), two equivalent Si(8), and two equivalent Si(9) atoms. There are twelve inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(9), one Si(10), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), two equivalent Mg(10), two equivalent Mg(5), two equivalent Mg(6), one Si(1), and one Si(9) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(4), two equivalent Mg(7), two equivalent Mg(8), one Si(11), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Mg(7), two equivalent Mg(8), one Si(12), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(10), one Mg(3), one Mg(6), two equivalent Si(12), and two equivalent Si(9) atoms. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(4), one Mg(5), one Mg(9), two equivalent Si(10), and two equivalent Si(11) atoms. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(4), two equivalent Mg(8), two equivalent Mg(9), one Si(10), and one Si(11) atom. In the eighth Si site, Si(8) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(10), two equivalent Mg(3), two equivalent Mg(7), one Si(12), and one Si(9) atom. In the ninth Si site, Si(9) is bonded in a 10-coordinate geometry to two equivalent Mg(10), two equivalent Mg(3), two equivalent Mg(6), one Si(2), one Si(8), and two equivalent Si(5) atoms. In the tenth Si site, Si(10) is bonded in a 10-coordinate geometry to two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(9), one Si(1), one Si(7), and two equivalent Si(6) atoms. In the eleventh Si site, Si(11) is bonded in a 8-coordinate geometry to two equivalent Mg(8), two equivalent Mg(9), one Si(3), one Si(7), and two equivalent Si(6) atoms. In the twelfth Si site, Si(12) is bonded in a 8-coordinate geometry to two equivalent Mg(10), two equivalent Mg(7), one Si(4), one Si(8), and two equivalent Si(5) atoms.
Mg5Si6 crystallizes in the monoclinic Pm space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 2-coordinate geometry to one Si(1) and one Si(2) atom. The Mg(1)-Si(1) bond length is 2.74 Å. The Mg(1)-Si(2) bond length is 2.99 Å. In the second Mg site, Mg(2) is bonded in a square co-planar geometry to one Si(3), one Si(4), one Si(7), and one Si(8) atom. The Mg(2)-Si(3) bond length is 2.81 Å. The Mg(2)-Si(4) bond length is 2.78 Å. The Mg(2)-Si(7) bond length is 2.80 Å. The Mg(2)-Si(8) bond length is 2.78 Å. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(5), two equivalent Si(4), two equivalent Si(8), and two equivalent Si(9) atoms. The Mg(3)-Si(5) bond length is 2.72 Å. Both Mg(3)-Si(4) bond lengths are 2.81 Å. Both Mg(3)-Si(8) bond lengths are 2.84 Å. Both Mg(3)-Si(9) bond lengths are 3.13 Å. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Si(6), two equivalent Si(10), two equivalent Si(3), and two equivalent Si(7) atoms. The Mg(4)-Si(6) bond length is 2.74 Å. Both Mg(4)-Si(10) bond lengths are 3.15 Å. Both Mg(4)-Si(3) bond lengths are 2.81 Å. Both Mg(4)-Si(7) bond lengths are 2.82 Å. In the fifth Mg site, Mg(5) is bonded in a 7-coordinate geometry to one Si(6), two equivalent Si(1), two equivalent Si(10), and two equivalent Si(2) atoms. The Mg(5)-Si(6) bond length is 2.71 Å. Both Mg(5)-Si(1) bond lengths are 2.84 Å. Both Mg(5)-Si(10) bond lengths are 2.94 Å. Both Mg(5)-Si(2) bond lengths are 2.71 Å. In the sixth Mg site, Mg(6) is bonded in a 7-coordinate geometry to one Si(5), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(9) atoms. The Mg(6)-Si(5) bond length is 2.71 Å. Both Mg(6)-Si(1) bond lengths are 2.77 Å. Both Mg(6)-Si(2) bond lengths are 2.94 Å. Both Mg(6)-Si(9) bond lengths are 2.88 Å. In the seventh Mg site, Mg(7) is bonded in a 8-coordinate geometry to two equivalent Si(12), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(8) atoms. Both Mg(7)-Si(12) bond lengths are 3.09 Å. Both Mg(7)-Si(3) bond lengths are 2.94 Å. Both Mg(7)-Si(4) bond lengths are 2.90 Å. Both Mg(7)-Si(8) bond lengths are 2.85 Å. In the eighth Mg site, Mg(8) is bonded in a 8-coordinate geometry to two equivalent Si(11), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(7) atoms. Both Mg(8)-Si(11) bond lengths are 3.07 Å. Both Mg(8)-Si(3) bond lengths are 2.90 Å. Both Mg(8)-Si(4) bond lengths are 2.94 Å. Both Mg(8)-Si(7) bond lengths are 2.88 Å. In the ninth Mg site, Mg(9) is bonded in a 9-coordinate geometry to one Si(6), two equivalent Si(1), two equivalent Si(10), two equivalent Si(11), and two equivalent Si(7) atoms. The Mg(9)-Si(6) bond length is 2.77 Å. Both Mg(9)-Si(1) bond lengths are 2.78 Å. Both Mg(9)-Si(10) bond lengths are 3.02 Å. Both Mg(9)-Si(11) bond lengths are 3.03 Å. Both Mg(9)-Si(7) bond lengths are 2.84 Å. In the tenth Mg site, Mg(10) is bonded in a 9-coordinate geometry to one Si(5), two equivalent Si(12), two equivalent Si(2), two equivalent Si(8), and two equivalent Si(9) atoms. The Mg(10)-Si(5) bond length is 2.75 Å. Both Mg(10)-Si(12) bond lengths are 2.99 Å. Both Mg(10)-Si(2) bond lengths are 2.76 Å. Both Mg(10)-Si(8) bond lengths are 2.81 Å. Both Mg(10)-Si(9) bond lengths are 3.00 Å. There are twelve inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), two equivalent Mg(5), two equivalent Mg(6), two equivalent Mg(9), one Si(10), and one Si(2) atom. The Si(1)-Si(10) bond length is 2.54 Å. The Si(1)-Si(2) bond length is 2.46 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(1), two equivalent Mg(10), two equivalent Mg(5), two equivalent Mg(6), one Si(1), and one Si(9) atom. The Si(2)-Si(9) bond length is 2.68 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(4), two equivalent Mg(7), two equivalent Mg(8), one Si(11), and one Si(4) atom. The Si(3)-Si(11) bond length is 2.48 Å. The Si(3)-Si(4) bond length is 2.39 Å. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Mg(7), two equivalent Mg(8), one Si(12), and one Si(3) atom. The Si(4)-Si(12) bond length is 2.48 Å. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(10), one Mg(3), one Mg(6), two equivalent Si(12), and two equivalent Si(9) atoms. Both Si(5)-Si(12) bond lengths are 2.56 Å. Both Si(5)-Si(9) bond lengths are 2.75 Å. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(4), one Mg(5), one Mg(9), two equivalent Si(10), and two equivalent Si(11) atoms. Both Si(6)-Si(10) bond lengths are 2.72 Å. Both Si(6)-Si(11) bond lengths are 2.57 Å. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(4), two equivalent Mg(8), two equivalent Mg(9), one Si(10), and one Si(11) atom. The Si(7)-Si(10) bond length is 2.43 Å. The Si(7)-Si(11) bond length is 2.46 Å. In the eighth Si site, Si(8) is bonded in a 9-coordinate geometry to one Mg(2), two equivalent Mg(10), two equivalent Mg(3), two equivalent Mg(7), one Si(12), and one Si(9) atom. The Si(8)-Si(12) bond length is 2.48 Å. The Si(8)-Si(9) bond length is 2.42 Å. In the ninth Si site, Si(9) is bonded in a 10-coordinate geometry to two equivalent Mg(10), two equivalent Mg(3), two equivalent Mg(6), one Si(2), one Si(8), and two equivalent Si(5) atoms. In the tenth Si site, Si(10) is bonded in a 10-coordinate geometry to two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(9), one Si(1), one Si(7), and two equivalent Si(6) atoms. In the eleventh Si site, Si(11) is bonded in a 8-coordinate geometry to two equivalent Mg(8), two equivalent Mg(9), one Si(3), one Si(7), and two equivalent Si(6) atoms. In the twelfth Si site, Si(12) is bonded in a 8-coordinate geometry to two equivalent Mg(10), two equivalent Mg(7), one Si(4), one Si(8), and two equivalent Si(5) atoms.