The crystal structure described by Mg5Si9 crystallizes in the triclinic P1 space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted bent 120 degrees geometry to one Mg(3), one Si(10), and one Si(8) atom. In the second Mg site, Mg(2) is bonded in a distorted single-bond geometry to one Mg(3), one Si(18), one Si(3), one Si(7), and one Si(9) atom. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one Mg(4), one Mg(5), one Si(14), one Si(17), and two equivalent Si(10) atoms. In the fourth Mg site, Mg(4) is bonded in a 2-coordinate geometry to one Mg(3), one Si(10), one Si(13), one Si(18), and one Si(3) atom. In the fifth Mg site, Mg(5) is bonded in a distorted single-bond geometry to one Mg(3), one Si(17), one Si(18), and one Si(4) atom. In the sixth Mg site, Mg(6) is bonded in a 2-coordinate geometry to one Si(17), one Si(18), one Si(3), one Si(5), and one Si(9) atom. In the seventh Mg site, Mg(7) is bonded in a 5-coordinate geometry to one Si(1), one Si(12), one Si(15), one Si(3), one Si(5), and one Si(9) atom. In the eighth Mg site, Mg(8) is bonded in a 2-coordinate geometry to one Si(15), one Si(16), and one Si(6) atom. In the ninth Mg site, Mg(9) is bonded in a 6-coordinate geometry to one Si(1), one Si(11), one Si(12), one Si(13), one Si(16), and one Si(7) atom. In the tenth Mg site, Mg(10) is bonded in a 2-coordinate geometry to one Si(17), one Si(2), and one Si(4) atom. There are eighteen inequivalent Si sites. In the first Si site, Si(1) is bonded in a 4-coordinate geometry to one Mg(7), one Mg(9), one Si(12), and one Si(7) atom. In the second Si site, Si(2) is bonded in a 1-coordinate geometry to one Mg(10), one Si(12), and one Si(14) atom. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(6), one Mg(7), one Si(18), one Si(5), and one Si(9) atom. In the fourth Si site, Si(4) is bonded in a 5-coordinate geometry to one Mg(10), one Mg(5), one Si(10), one Si(14), and one Si(17) atom. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(6), one Mg(7), one Si(12), one Si(13), one Si(18), one Si(3), one Si(7), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 1-coordinate geometry to one Mg(8) and one Si(11) atom. In the seventh Si site, Si(7) is bonded in a 2-coordinate geometry to one Mg(2), one Mg(9), one Si(1), one Si(5), and one Si(9) atom. In the eighth Si site, Si(8) is bonded in a distorted single-bond geometry to one Mg(1) and one Si(11) atom. In the ninth Si site, Si(9) is bonded in a 6-coordinate geometry to one Mg(2), one Mg(6), one Mg(7), one Si(3), one Si(5), and one Si(7) atom. In the tenth Si site, Si(10) is bonded in a distorted bent 120 degrees geometry to one Mg(1), one Mg(4), two equivalent Mg(3), and one Si(4) atom. In the eleventh Si site, Si(11) is bonded in a 4-coordinate geometry to one Mg(9), one Si(15), one Si(6), and one Si(8) atom. In the twelfth Si site, Si(12) is bonded in a 6-coordinate geometry to one Mg(7), one Mg(9), one Si(1), one Si(16), one Si(2), and one Si(5) atom. In the thirteenth Si site, Si(13) is bonded in a 2-coordinate geometry to one Mg(4), one Mg(9), and one Si(5) atom. In the fourteenth Si site, Si(14) is bonded in a 3-coordinate geometry to one Mg(3), one Si(2), and one Si(4) atom. In the fifteenth Si site, Si(15) is bonded in a 4-coordinate geometry to one Mg(7), one Mg(8), one Si(11), and one Si(16) atom. In the sixteenth Si site, Si(16) is bonded in a 2-coordinate geometry to one Mg(8), one Mg(9), one Si(12), and one Si(15) atom. In the seventeenth Si site, Si(17) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(3), one Mg(5), one Mg(6), one Si(18), and one Si(4) atom. In the eighteenth Si site, Si(18) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), one Mg(6), one Si(17), one Si(3), and one Si(5) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg5Si9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.730
_cell_length_b   6.919
_cell_length_c   13.601
_cell_angle_alpha   104.121
_cell_angle_beta   92.061
_cell_angle_gamma   108.053
_symmetry_Int_Tables_number   1
_cell_volume   493.526
_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  0.427  0.761  0.674  1.0
  Mg  Mg1  1  0.759  0.444  0.383  1.0
  Mg  Mg2  1  0.649  0.584  0.546  1.0
  Mg  Mg3  1  0.224  0.321  0.407  1.0
  Mg  Mg4  1  0.042  0.007  0.619  1.0
  Mg  Mg5  1  0.165  0.846  0.445  1.0
  Mg  Mg6  1  0.497  0.527  0.142  1.0
  Mg  Mg7  1  0.189  0.387  0.922  1.0
  Mg  Mg8  1  0.444  1.000  0.112  1.0
  Mg  Mg9  1  0.410  0.299  0.756  1.0
  Si  Si10  1  0.072  0.184  0.122  1.0
  Si  Si11  1  0.657  0.654  0.862  1.0
  Si  Si12  1  0.477  0.744  0.330  1.0
  Si  Si13  1  0.845  0.274  0.690  1.0
  Si  Si14  1  0.866  0.850  0.250  1.0
  Si  Si15  1  0.950  0.014  0.840  1.0
  Si  Si16  1  0.804  0.232  0.245  1.0
  Si  Si17  1  0.302  0.855  0.838  1.0
  Si  Si18  1  0.074  0.600  0.224  1.0
  Si  Si19  1  0.141  0.463  0.569  1.0
  Si  Si20  1  0.659  0.099  0.931  1.0
  Si  Si21  1  0.872  0.865  0.061  1.0
  Si  Si22  1  0.359  0.124  0.277  1.0
  Si  Si23  1  0.894  0.608  0.742  1.0
  Si  Si24  1  0.776  0.401  0.021  1.0
  Si  Si25  1  0.151  0.705  0.010  1.0
  Si  Si26  1  0.551  0.136  0.548  1.0
  Si  Si27  1  0.745  0.015  0.433  1.0
[/CIF]
.
The crystal structure described by Mg5Si9 crystallizes in the triclinic P1 space group. There are ten inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted bent 120 degrees geometry to one Mg(3), one Si(10), and one Si(8) atom. In the second Mg site, Mg(2) is bonded in a distorted single-bond geometry to one Mg(3), one Si(18), one Si(3), one Si(7), and one Si(9) atom. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one Mg(4), one Mg(5), one Si(14), one Si(17), and two equivalent Si(10) atoms. In the fourth Mg site, Mg(4) is bonded in a 2-coordinate geometry to one Mg(3), one Si(10), one Si(13), one Si(18), and one Si(3) atom. In the fifth Mg site, Mg(5) is bonded in a distorted single-bond geometry to one Mg(3), one Si(17), one Si(18), and one Si(4) atom. In the sixth Mg site, Mg(6) is bonded in a 2-coordinate geometry to one Si(17), one Si(18), one Si(3), one Si(5), and one Si(9) atom. In the seventh Mg site, Mg(7) is bonded in a 5-coordinate geometry to one Si(1), one Si(12), one Si(15), one Si(3), one Si(5), and one Si(9) atom. In the eighth Mg site, Mg(8) is bonded in a 2-coordinate geometry to one Si(15), one Si(16), and one Si(6) atom. In the ninth Mg site, Mg(9) is bonded in a 6-coordinate geometry to one Si(1), one Si(11), one Si(12), one Si(13), one Si(16), and one Si(7) atom. In the tenth Mg site, Mg(10) is bonded in a 2-coordinate geometry to one Si(17), one Si(2), and one Si(4) atom. There are eighteen inequivalent Si sites. In the first Si site, Si(1) is bonded in a 4-coordinate geometry to one Mg(7), one Mg(9), one Si(12), and one Si(7) atom. In the second Si site, Si(2) is bonded in a 1-coordinate geometry to one Mg(10), one Si(12), and one Si(14) atom. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(6), one Mg(7), one Si(18), one Si(5), and one Si(9) atom. In the fourth Si site, Si(4) is bonded in a 5-coordinate geometry to one Mg(10), one Mg(5), one Si(10), one Si(14), and one Si(17) atom. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(6), one Mg(7), one Si(12), one Si(13), one Si(18), one Si(3), one Si(7), and one Si(9) atom. In the sixth Si site, Si(6) is bonded in a 1-coordinate geometry to one Mg(8) and one Si(11) atom. In the seventh Si site, Si(7) is bonded in a 2-coordinate geometry to one Mg(2), one Mg(9), one Si(1), one Si(5), and one Si(9) atom. In the eighth Si site, Si(8) is bonded in a distorted single-bond geometry to one Mg(1) and one Si(11) atom. In the ninth Si site, Si(9) is bonded in a 6-coordinate geometry to one Mg(2), one Mg(6), one Mg(7), one Si(3), one Si(5), and one Si(7) atom. In the tenth Si site, Si(10) is bonded in a distorted bent 120 degrees geometry to one Mg(1), one Mg(4), two equivalent Mg(3), and one Si(4) atom. In the eleventh Si site, Si(11) is bonded in a 4-coordinate geometry to one Mg(9), one Si(15), one Si(6), and one Si(8) atom. In the twelfth Si site, Si(12) is bonded in a 6-coordinate geometry to one Mg(7), one Mg(9), one Si(1), one Si(16), one Si(2), and one Si(5) atom. In the thirteenth Si site, Si(13) is bonded in a 2-coordinate geometry to one Mg(4), one Mg(9), and one Si(5) atom. In the fourteenth Si site, Si(14) is bonded in a 3-coordinate geometry to one Mg(3), one Si(2), and one Si(4) atom. In the fifteenth Si site, Si(15) is bonded in a 4-coordinate geometry to one Mg(7), one Mg(8), one Si(11), and one Si(16) atom. In the sixteenth Si site, Si(16) is bonded in a 2-coordinate geometry to one Mg(8), one Mg(9), one Si(12), and one Si(15) atom. In the seventeenth Si site, Si(17) is bonded in a 6-coordinate geometry to one Mg(10), one Mg(3), one Mg(5), one Mg(6), one Si(18), and one Si(4) atom. In the eighteenth Si site, Si(18) is bonded in a 7-coordinate geometry to one Mg(2), one Mg(4), one Mg(5), one Mg(6), one Si(17), one Si(3), and one Si(5) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg5Si9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.730
_cell_length_b   6.919
_cell_length_c   13.601
_cell_angle_alpha   104.121
_cell_angle_beta   92.061
_cell_angle_gamma   108.053
_symmetry_Int_Tables_number   1
_cell_volume   493.526
_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  0.427  0.761  0.674  1.0
  Mg  Mg1  1  0.759  0.444  0.383  1.0
  Mg  Mg2  1  0.649  0.584  0.546  1.0
  Mg  Mg3  1  0.224  0.321  0.407  1.0
  Mg  Mg4  1  0.042  0.007  0.619  1.0
  Mg  Mg5  1  0.165  0.846  0.445  1.0
  Mg  Mg6  1  0.497  0.527  0.142  1.0
  Mg  Mg7  1  0.189  0.387  0.922  1.0
  Mg  Mg8  1  0.444  1.000  0.112  1.0
  Mg  Mg9  1  0.410  0.299  0.756  1.0
  Si  Si10  1  0.072  0.184  0.122  1.0
  Si  Si11  1  0.657  0.654  0.862  1.0
  Si  Si12  1  0.477  0.744  0.330  1.0
  Si  Si13  1  0.845  0.274  0.690  1.0
  Si  Si14  1  0.866  0.850  0.250  1.0
  Si  Si15  1  0.950  0.014  0.840  1.0
  Si  Si16  1  0.804  0.232  0.245  1.0
  Si  Si17  1  0.302  0.855  0.838  1.0
  Si  Si18  1  0.074  0.600  0.224  1.0
  Si  Si19  1  0.141  0.463  0.569  1.0
  Si  Si20  1  0.659  0.099  0.931  1.0
  Si  Si21  1  0.872  0.865  0.061  1.0
  Si  Si22  1  0.359  0.124  0.277  1.0
  Si  Si23  1  0.894  0.608  0.742  1.0
  Si  Si24  1  0.776  0.401  0.021  1.0
  Si  Si25  1  0.151  0.705  0.010  1.0
  Si  Si26  1  0.551  0.136  0.548  1.0
  Si  Si27  1  0.745  0.015  0.433  1.0
[/CIF]
.