Mg6Si5 crystallizes in the monoclinic Pm space group. There are twelve inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(9), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Mg site, Mg(2) is bonded in a 2-coordinate geometry to one Si(1), one Si(10), one Si(2), two equivalent Si(5), and two equivalent Si(6) atoms. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Si(3), one Si(6), one Si(7), two equivalent Si(10), and two equivalent Si(2) atoms. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one Si(9), two equivalent Si(4), two equivalent Si(5), and two equivalent Si(8) atoms. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(1), two equivalent Si(4), and two equivalent Si(5) atoms. In the sixth Mg site, Mg(6) is bonded in a 7-coordinate geometry to one Si(2), two equivalent Si(3), two equivalent Si(6), and two equivalent Si(7) atoms. In the seventh Mg site, Mg(7) is bonded in a 6-coordinate geometry to one Si(6), one Si(8), two equivalent Si(1), and two equivalent Si(10) atoms. In the eighth Mg site, Mg(8) is bonded in a 7-coordinate geometry to one Si(5), one Si(6), one Si(8), two equivalent Si(1), and two equivalent Si(2) atoms. In the ninth Mg site, Mg(9) is bonded to one Si(4), one Si(5), and two equivalent Si(9) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. In the tenth Mg site, Mg(10) is bonded in a 6-coordinate geometry to one Si(10), one Si(9), two equivalent Si(3), and two equivalent Si(7) atoms. In the eleventh Mg site, Mg(11) is bonded to one Si(3), one Si(7), and two equivalent Si(9) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. In the twelfth Mg site, Mg(12) is bonded to one Si(3), one Si(4), and two equivalent Si(9) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(5), two equivalent Mg(7), two equivalent Mg(8), one Si(2), and two equivalent Si(8) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), two equivalent Mg(8), one Si(1), and two equivalent Si(6) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(11), one Mg(12), one Mg(3), two equivalent Mg(1), two equivalent Mg(10), and two equivalent Mg(6) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(12), one Mg(9), two equivalent Mg(1), two equivalent Mg(4), two equivalent Mg(5), and one Si(8) atom. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to one Mg(8), one Mg(9), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), and one Si(8) atom. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to one Mg(3), one Mg(7), one Mg(8), two equivalent Mg(2), two equivalent Mg(6), one Si(7), and two equivalent Si(2) atoms. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(11), one Mg(3), two equivalent Mg(10), two equivalent Mg(6), one Si(6), and two equivalent Si(10) atoms. In the eighth Si site, Si(8) is bonded in a 8-coordinate geometry to one Mg(7), one Mg(8), two equivalent Mg(4), one Si(4), one Si(5), and two equivalent Si(1) atoms. In the ninth Si site, Si(9) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(10), one Mg(4), two equivalent Mg(11), two equivalent Mg(12), and two equivalent Mg(9) atoms. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(2), two equivalent Mg(3), two equivalent Mg(7), and two equivalent Si(7) atoms.
Mg6Si5 crystallizes in the monoclinic Pm space group. There are twelve inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(9), two equivalent Si(3), and two equivalent Si(4) atoms. The Mg(1)-Si(9) bond length is 2.88 Å. Both Mg(1)-Si(3) bond lengths are 2.99 Å. Both Mg(1)-Si(4) bond lengths are 2.90 Å. In the second Mg site, Mg(2) is bonded in a 2-coordinate geometry to one Si(1), one Si(10), one Si(2), two equivalent Si(5), and two equivalent Si(6) atoms. The Mg(2)-Si(1) bond length is 3.10 Å. The Mg(2)-Si(10) bond length is 3.12 Å. The Mg(2)-Si(2) bond length is 3.01 Å. Both Mg(2)-Si(5) bond lengths are 2.83 Å. Both Mg(2)-Si(6) bond lengths are 3.07 Å. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Si(3), one Si(6), one Si(7), two equivalent Si(10), and two equivalent Si(2) atoms. The Mg(3)-Si(3) bond length is 2.69 Å. The Mg(3)-Si(6) bond length is 2.96 Å. The Mg(3)-Si(7) bond length is 2.89 Å. Both Mg(3)-Si(10) bond lengths are 3.00 Å. Both Mg(3)-Si(2) bond lengths are 2.84 Å. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one Si(9), two equivalent Si(4), two equivalent Si(5), and two equivalent Si(8) atoms. The Mg(4)-Si(9) bond length is 2.92 Å. Both Mg(4)-Si(4) bond lengths are 3.01 Å. Both Mg(4)-Si(5) bond lengths are 3.00 Å. Both Mg(4)-Si(8) bond lengths are 2.80 Å. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(1), two equivalent Si(4), and two equivalent Si(5) atoms. The Mg(5)-Si(1) bond length is 2.76 Å. Both Mg(5)-Si(4) bond lengths are 2.95 Å. Both Mg(5)-Si(5) bond lengths are 3.01 Å. In the sixth Mg site, Mg(6) is bonded in a 7-coordinate geometry to one Si(2), two equivalent Si(3), two equivalent Si(6), and two equivalent Si(7) atoms. The Mg(6)-Si(2) bond length is 2.93 Å. Both Mg(6)-Si(3) bond lengths are 2.95 Å. Both Mg(6)-Si(6) bond lengths are 3.12 Å. Both Mg(6)-Si(7) bond lengths are 2.98 Å. In the seventh Mg site, Mg(7) is bonded in a 6-coordinate geometry to one Si(6), one Si(8), two equivalent Si(1), and two equivalent Si(10) atoms. The Mg(7)-Si(6) bond length is 3.01 Å. The Mg(7)-Si(8) bond length is 2.90 Å. Both Mg(7)-Si(1) bond lengths are 2.83 Å. Both Mg(7)-Si(10) bond lengths are 2.86 Å. In the eighth Mg site, Mg(8) is bonded in a 7-coordinate geometry to one Si(5), one Si(6), one Si(8), two equivalent Si(1), and two equivalent Si(2) atoms. The Mg(8)-Si(5) bond length is 2.75 Å. The Mg(8)-Si(6) bond length is 2.78 Å. The Mg(8)-Si(8) bond length is 2.91 Å. Both Mg(8)-Si(1) bond lengths are 2.79 Å. Both Mg(8)-Si(2) bond lengths are 2.86 Å. In the ninth Mg site, Mg(9) is bonded to one Si(4), one Si(5), and two equivalent Si(9) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. The Mg(9)-Si(4) bond length is 2.67 Å. The Mg(9)-Si(5) bond length is 2.70 Å. Both Mg(9)-Si(9) bond lengths are 2.72 Å. In the tenth Mg site, Mg(10) is bonded in a 6-coordinate geometry to one Si(10), one Si(9), two equivalent Si(3), and two equivalent Si(7) atoms. The Mg(10)-Si(10) bond length is 2.87 Å. The Mg(10)-Si(9) bond length is 2.93 Å. Both Mg(10)-Si(3) bond lengths are 2.86 Å. Both Mg(10)-Si(7) bond lengths are 3.03 Å. In the eleventh Mg site, Mg(11) is bonded to one Si(3), one Si(7), and two equivalent Si(9) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. The Mg(11)-Si(3) bond length is 2.66 Å. The Mg(11)-Si(7) bond length is 2.64 Å. Both Mg(11)-Si(9) bond lengths are 2.73 Å. In the twelfth Mg site, Mg(12) is bonded to one Si(3), one Si(4), and two equivalent Si(9) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. The Mg(12)-Si(3) bond length is 2.67 Å. The Mg(12)-Si(4) bond length is 2.66 Å. Both Mg(12)-Si(9) bond lengths are 2.75 Å. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(5), two equivalent Mg(7), two equivalent Mg(8), one Si(2), and two equivalent Si(8) atoms. The Si(1)-Si(2) bond length is 2.82 Å. Both Si(1)-Si(8) bond lengths are 2.50 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), two equivalent Mg(8), one Si(1), and two equivalent Si(6) atoms. Both Si(2)-Si(6) bond lengths are 2.71 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to one Mg(11), one Mg(12), one Mg(3), two equivalent Mg(1), two equivalent Mg(10), and two equivalent Mg(6) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to one Mg(12), one Mg(9), two equivalent Mg(1), two equivalent Mg(4), two equivalent Mg(5), and one Si(8) atom. The Si(4)-Si(8) bond length is 2.41 Å. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to one Mg(8), one Mg(9), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), and one Si(8) atom. The Si(5)-Si(8) bond length is 2.48 Å. In the sixth Si site, Si(6) is bonded in a 10-coordinate geometry to one Mg(3), one Mg(7), one Mg(8), two equivalent Mg(2), two equivalent Mg(6), one Si(7), and two equivalent Si(2) atoms. The Si(6)-Si(7) bond length is 2.44 Å. In the seventh Si site, Si(7) is bonded in a 9-coordinate geometry to one Mg(11), one Mg(3), two equivalent Mg(10), two equivalent Mg(6), one Si(6), and two equivalent Si(10) atoms. Both Si(7)-Si(10) bond lengths are 2.51 Å. In the eighth Si site, Si(8) is bonded in a 8-coordinate geometry to one Mg(7), one Mg(8), two equivalent Mg(4), one Si(4), one Si(5), and two equivalent Si(1) atoms. In the ninth Si site, Si(9) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(10), one Mg(4), two equivalent Mg(11), two equivalent Mg(12), and two equivalent Mg(9) atoms. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(2), two equivalent Mg(3), two equivalent Mg(7), and two equivalent Si(7) atoms.