The crystal structure described by 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 bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the second Mg site, Mg(2) is bonded in a rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(5), and one Si(6) atom. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Si(3), 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 5-coordinate geometry to one Si(5), one Si(8), one Si(9), and two equivalent Si(1) atoms. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Si(4), one Si(9), and two equivalent Si(8) atoms. In the sixth Mg site, Mg(6) is bonded in a 4-coordinate geometry to one Si(10), one Si(3), one Si(6), and two equivalent Si(7) atoms. In the seventh Mg site, Mg(7) is bonded in a 5-coordinate geometry to one Si(1), one Si(2), one Si(7), and two equivalent Si(6) atoms. In the eighth Mg site, Mg(8) is bonded in a 4-coordinate geometry to one Si(1), one Si(2), one Si(5), and one Si(8) atom. In the ninth Mg site, Mg(9) is bonded in a 2-coordinate geometry to one Si(4) and one Si(9) atom. In the tenth Mg site, Mg(10) is bonded in a 5-coordinate geometry to one Si(10), two equivalent Si(3), and two equivalent Si(7) atoms. In the eleventh Mg site, Mg(11) is bonded in a single-bond geometry to one Si(7) atom. In the twelfth Mg site, Mg(12) is bonded in a 2-coordinate geometry to one Si(9) and two equivalent Si(4) atoms. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(7), one Mg(8), two equivalent Mg(4), one Si(2), and one Si(8) atom. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(7), one Mg(8), two equivalent Mg(3), one Si(1), and one Si(10) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(6), two equivalent Mg(10), one Si(7), and two equivalent Si(10) atoms. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(5), one Mg(9), two equivalent Mg(12), one Si(5), and one Si(9) atom. In the fifth Si site, Si(5) is bonded in a 6-coordinate geometry to one Mg(2), one Mg(4), one Mg(8), one Si(4), one Si(8), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), two equivalent Mg(7), one Si(10), and one Si(7) atom. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to one Mg(11), one Mg(7), two equivalent Mg(10), two equivalent Mg(6), one Si(3), and one Si(6) atom. In the eighth Si site, Si(8) is bonded in a 6-coordinate geometry to one Mg(4), one Mg(8), two equivalent Mg(5), one Si(1), and one Si(5) atom. In the ninth Si site, Si(9) is bonded in a 6-coordinate geometry to one Mg(12), one Mg(4), one Mg(5), one Mg(9), one Si(4), and one Si(5) atom. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(6), two equivalent Mg(3), one Si(2), one Si(6), and two equivalent Si(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg6Si5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.679
_cell_length_b   6.703
_cell_length_c   14.345
_cell_angle_alpha   98.659
_cell_angle_beta   92.172
_cell_angle_gamma   96.885
_symmetry_Int_Tables_number   1
_cell_volume   440.866
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Mg  Mg0  1  0.794  0.053  0.026  1.0
  Mg  Mg1  1  0.187  0.916  0.509  1.0
  Mg  Mg2  1  0.721  0.044  0.381  1.0
  Mg  Mg3  1  0.661  0.773  0.634  1.0
  Mg  Mg4  1  0.767  0.507  0.802  1.0
  Mg  Mg5  1  0.381  0.826  0.147  1.0
  Mg  Mg6  1  0.644  0.581  0.397  1.0
  Mg  Mg7  1  0.738  0.241  0.589  1.0
  Mg  Mg8  1  0.311  0.765  0.922  1.0
  Mg  Mg9  1  0.275  0.355  0.130  1.0
  Mg  Mg10  1  0.797  0.566  0.017  1.0
  Mg  Mg11  1  0.210  0.288  0.908  1.0
  Si  Si12  1  0.134  0.549  0.549  1.0
  Si  Si13  1  0.276  0.271  0.448  1.0
  Si  Si14  1  0.744  0.213  0.219  1.0
  Si  Si15  1  0.610  0.074  0.831  1.0
  Si  Si16  1  0.287  0.096  0.691  1.0
  Si  Si17  1  0.157  0.790  0.320  1.0
  Si  Si18  1  0.825  0.575  0.203  1.0
  Si  Si19  1  0.251  0.457  0.706  1.0
  Si  Si20  1  0.016  0.910  0.794  1.0
  Si  Si21  1  0.210  0.150  0.281  1.0
[/CIF]
.
The crystal structure described by 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 bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the second Mg site, Mg(2) is bonded in a rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(5), and one Si(6) atom. In the third Mg site, Mg(3) is bonded in a 7-coordinate geometry to one Si(3), 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 5-coordinate geometry to one Si(5), one Si(8), one Si(9), and two equivalent Si(1) atoms. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Si(4), one Si(9), and two equivalent Si(8) atoms. In the sixth Mg site, Mg(6) is bonded in a 4-coordinate geometry to one Si(10), one Si(3), one Si(6), and two equivalent Si(7) atoms. In the seventh Mg site, Mg(7) is bonded in a 5-coordinate geometry to one Si(1), one Si(2), one Si(7), and two equivalent Si(6) atoms. In the eighth Mg site, Mg(8) is bonded in a 4-coordinate geometry to one Si(1), one Si(2), one Si(5), and one Si(8) atom. In the ninth Mg site, Mg(9) is bonded in a 2-coordinate geometry to one Si(4) and one Si(9) atom. In the tenth Mg site, Mg(10) is bonded in a 5-coordinate geometry to one Si(10), two equivalent Si(3), and two equivalent Si(7) atoms. In the eleventh Mg site, Mg(11) is bonded in a single-bond geometry to one Si(7) atom. In the twelfth Mg site, Mg(12) is bonded in a 2-coordinate geometry to one Si(9) and two equivalent Si(4) atoms. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(7), one Mg(8), two equivalent Mg(4), one Si(2), and one Si(8) atom. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(7), one Mg(8), two equivalent Mg(3), one Si(1), and one Si(10) atom. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one Mg(6), two equivalent Mg(10), one Si(7), and two equivalent Si(10) atoms. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(5), one Mg(9), two equivalent Mg(12), one Si(5), and one Si(9) atom. In the fifth Si site, Si(5) is bonded in a 6-coordinate geometry to one Mg(2), one Mg(4), one Mg(8), one Si(4), one Si(8), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(6), two equivalent Mg(3), two equivalent Mg(7), one Si(10), and one Si(7) atom. In the seventh Si site, Si(7) is bonded in a 8-coordinate geometry to one Mg(11), one Mg(7), two equivalent Mg(10), two equivalent Mg(6), one Si(3), and one Si(6) atom. In the eighth Si site, Si(8) is bonded in a 6-coordinate geometry to one Mg(4), one Mg(8), two equivalent Mg(5), one Si(1), and one Si(5) atom. In the ninth Si site, Si(9) is bonded in a 6-coordinate geometry to one Mg(12), one Mg(4), one Mg(5), one Mg(9), one Si(4), and one Si(5) atom. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(10), one Mg(6), two equivalent Mg(3), one Si(2), one Si(6), and two equivalent Si(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg6Si5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.679
_cell_length_b   6.703
_cell_length_c   14.345
_cell_angle_alpha   98.659
_cell_angle_beta   92.172
_cell_angle_gamma   96.885
_symmetry_Int_Tables_number   1
_cell_volume   440.866
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Mg  Mg0  1  0.794  0.053  0.026  1.0
  Mg  Mg1  1  0.187  0.916  0.509  1.0
  Mg  Mg2  1  0.721  0.044  0.381  1.0
  Mg  Mg3  1  0.661  0.773  0.634  1.0
  Mg  Mg4  1  0.767  0.507  0.802  1.0
  Mg  Mg5  1  0.381  0.826  0.147  1.0
  Mg  Mg6  1  0.644  0.581  0.397  1.0
  Mg  Mg7  1  0.738  0.241  0.589  1.0
  Mg  Mg8  1  0.311  0.765  0.922  1.0
  Mg  Mg9  1  0.275  0.355  0.130  1.0
  Mg  Mg10  1  0.797  0.566  0.017  1.0
  Mg  Mg11  1  0.210  0.288  0.908  1.0
  Si  Si12  1  0.134  0.549  0.549  1.0
  Si  Si13  1  0.276  0.271  0.448  1.0
  Si  Si14  1  0.744  0.213  0.219  1.0
  Si  Si15  1  0.610  0.074  0.831  1.0
  Si  Si16  1  0.287  0.096  0.691  1.0
  Si  Si17  1  0.157  0.790  0.320  1.0
  Si  Si18  1  0.825  0.575  0.203  1.0
  Si  Si19  1  0.251  0.457  0.706  1.0
  Si  Si20  1  0.016  0.910  0.794  1.0
  Si  Si21  1  0.210  0.150  0.281  1.0
[/CIF]
.