The crystal structure described by Mg5Si6 crystallizes in the triclinic P1 space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(11), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one Si(10), one Si(12), one Si(4), one Si(7), and two equivalent Si(3) atoms. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Si(12), one Si(3), one Si(4), one Si(5), one Si(8), and one Si(9) atom. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Si(10), one Si(11), one Si(12), one Si(3), one Si(6), and one Si(7) atom. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Si(1), one Si(10), one Si(11), one Si(6), and one Si(7) atom. In the sixth Mg site, Mg(6) is bonded in a 3-coordinate geometry to one Si(1), one Si(5), and one Si(8) atom. In the seventh Mg site, Mg(7) is bonded in a 5-coordinate geometry to one Si(12), one Si(3), one Si(4), one Si(5), and one Si(8) atom. In the eighth Mg site, Mg(8) is bonded in a 5-coordinate geometry to one Si(10), one Si(11), one Si(12), one Si(4), one Si(6), and one Si(7) atom. In the ninth Mg site, Mg(9) is bonded in a 6-coordinate geometry to one Si(1), one Si(10), one Si(11), one Si(2), one Si(6), and one Si(7) atom. In the tenth Mg site, Mg(10) is bonded in a 4-coordinate geometry to one Si(1), one Si(2), one Si(5), one Si(8), and one Si(9) atom. There are twelve inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(5), one Mg(6), one Mg(9), one Si(2), and one Si(9) atom. In the second Si site, Si(2) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(9), two equivalent Mg(1), one Si(1), and one Si(10) atom. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to one Mg(3), one Mg(4), one Mg(7), two equivalent Mg(2), one Si(11), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(7), one Mg(8), one Si(12), one Si(3), and one Si(8) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(10), one Mg(3), one Mg(6), one Mg(7), one Si(8), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(10), and one Si(11) atom. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(10), and one Si(11) atom. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(10), one Mg(3), one Mg(6), one Mg(7), one Si(4), one Si(5), and one Si(9) atom. In the ninth Si site, Si(9) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(3), one Si(1), one Si(12), one Si(5), and one Si(8) atom. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(2), one Si(6), and one Si(7) atom. In the eleventh Si site, Si(11) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(3), one Si(6), and one Si(7) atom. In the twelfth Si site, Si(12) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(7), one Mg(8), one Si(4), and one Si(9) atom. is represented by the CIF file [CIF]
data_Mg5Si6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.852
_cell_length_b   5.904
_cell_length_c   12.204
_cell_angle_alpha   89.203
_cell_angle_beta   88.237
_cell_angle_gamma   89.156
_symmetry_Int_Tables_number   1
_cell_volume   421.351
_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  0.859  0.181  0.040  1.0
  Mg  Mg1  1  0.328  0.220  0.466  1.0
  Mg  Mg2  1  0.046  0.446  0.655  1.0
  Mg  Mg3  1  0.067  0.665  0.394  1.0
  Mg  Mg4  1  0.093  0.623  0.112  1.0
  Mg  Mg5  1  0.777  0.669  0.868  1.0
  Mg  Mg6  1  0.815  0.930  0.621  1.0
  Mg  Mg7  1  0.573  0.794  0.385  1.0
  Mg  Mg8  1  0.598  0.717  0.111  1.0
  Mg  Mg9  1  0.259  0.416  0.894  1.0
  Si  Si10  1  0.335  0.846  0.932  1.0
  Si  Si11  1  0.382  0.153  0.060  1.0
  Si  Si12  1  0.813  0.271  0.464  1.0
  Si  Si13  1  0.603  0.524  0.589  1.0
  Si  Si14  1  0.921  0.129  0.821  1.0
  Si  Si15  1  0.890  0.972  0.245  1.0
  Si  Si16  1  0.383  0.442  0.263  1.0
  Si  Si17  1  0.579  0.289  0.745  1.0
  Si  Si18  1  0.290  0.003  0.745  1.0
  Si  Si19  1  0.297  0.040  0.246  1.0
  Si  Si20  1  0.796  0.368  0.266  1.0
  Si  Si21  1  0.294  0.800  0.576  1.0
[/CIF]
.
The crystal structure described by Mg5Si6 crystallizes in the triclinic P1 space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one Si(11), one Si(5), one Si(6), and two equivalent Si(2) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one Si(10), one Si(12), one Si(4), one Si(7), and two equivalent Si(3) atoms. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Si(12), one Si(3), one Si(4), one Si(5), one Si(8), and one Si(9) atom. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Si(10), one Si(11), one Si(12), one Si(3), one Si(6), and one Si(7) atom. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Si(1), one Si(10), one Si(11), one Si(6), and one Si(7) atom. In the sixth Mg site, Mg(6) is bonded in a 3-coordinate geometry to one Si(1), one Si(5), and one Si(8) atom. In the seventh Mg site, Mg(7) is bonded in a 5-coordinate geometry to one Si(12), one Si(3), one Si(4), one Si(5), and one Si(8) atom. In the eighth Mg site, Mg(8) is bonded in a 5-coordinate geometry to one Si(10), one Si(11), one Si(12), one Si(4), one Si(6), and one Si(7) atom. In the ninth Mg site, Mg(9) is bonded in a 6-coordinate geometry to one Si(1), one Si(10), one Si(11), one Si(2), one Si(6), and one Si(7) atom. In the tenth Mg site, Mg(10) is bonded in a 4-coordinate geometry to one Si(1), one Si(2), one Si(5), one Si(8), and one Si(9) atom. There are twelve inequivalent Si sites. In the first Si site, Si(1) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(5), one Mg(6), one Mg(9), one Si(2), and one Si(9) atom. In the second Si site, Si(2) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(9), two equivalent Mg(1), one Si(1), and one Si(10) atom. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to one Mg(3), one Mg(4), one Mg(7), two equivalent Mg(2), one Si(11), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(7), one Mg(8), one Si(12), one Si(3), and one Si(8) atom. In the fifth Si site, Si(5) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(10), one Mg(3), one Mg(6), one Mg(7), one Si(8), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(10), and one Si(11) atom. In the seventh Si site, Si(7) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(10), and one Si(11) atom. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(10), one Mg(3), one Mg(6), one Mg(7), one Si(4), one Si(5), and one Si(9) atom. In the ninth Si site, Si(9) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(3), one Si(1), one Si(12), one Si(5), and one Si(8) atom. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(2), one Si(6), and one Si(7) atom. In the eleventh Si site, Si(11) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), one Mg(8), one Mg(9), one Si(3), one Si(6), and one Si(7) atom. In the twelfth Si site, Si(12) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(3), one Mg(4), one Mg(7), one Mg(8), one Si(4), and one Si(9) atom. is represented by the CIF file [CIF]
data_Mg5Si6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.852
_cell_length_b   5.904
_cell_length_c   12.204
_cell_angle_alpha   89.203
_cell_angle_beta   88.237
_cell_angle_gamma   89.156
_symmetry_Int_Tables_number   1
_cell_volume   421.351
_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  0.859  0.181  0.040  1.0
  Mg  Mg1  1  0.328  0.220  0.466  1.0
  Mg  Mg2  1  0.046  0.446  0.655  1.0
  Mg  Mg3  1  0.067  0.665  0.394  1.0
  Mg  Mg4  1  0.093  0.623  0.112  1.0
  Mg  Mg5  1  0.777  0.669  0.868  1.0
  Mg  Mg6  1  0.815  0.930  0.621  1.0
  Mg  Mg7  1  0.573  0.794  0.385  1.0
  Mg  Mg8  1  0.598  0.717  0.111  1.0
  Mg  Mg9  1  0.259  0.416  0.894  1.0
  Si  Si10  1  0.335  0.846  0.932  1.0
  Si  Si11  1  0.382  0.153  0.060  1.0
  Si  Si12  1  0.813  0.271  0.464  1.0
  Si  Si13  1  0.603  0.524  0.589  1.0
  Si  Si14  1  0.921  0.129  0.821  1.0
  Si  Si15  1  0.890  0.972  0.245  1.0
  Si  Si16  1  0.383  0.442  0.263  1.0
  Si  Si17  1  0.579  0.289  0.745  1.0
  Si  Si18  1  0.290  0.003  0.745  1.0
  Si  Si19  1  0.297  0.040  0.246  1.0
  Si  Si20  1  0.796  0.368  0.266  1.0
  Si  Si21  1  0.294  0.800  0.576  1.0
[/CIF]
.