The crystal structure described by Mg9Si5 crystallizes in the trigonal R32 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Si(2), one Si(3), one Si(4), and one Si(5) atom to form a mixture of distorted corner and edge-sharing MgSi4 tetrahedra. In the second Mg site, Mg(2) is bonded to two equivalent Si(2) and two equivalent Si(3) atoms to form a mixture of distorted corner and edge-sharing MgSi4 tetrahedra. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(2), one Si(4), one Si(5), and two equivalent Si(1) atoms. In the fourth Mg site, Mg(4) is bonded to two equivalent Si(1) and two equivalent Si(5) atoms to form a mixture of distorted corner and edge-sharing MgSi4 tetrahedra. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Mg(4) and six equivalent Mg(3) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), and three equivalent Mg(3) atoms. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to three equivalent Mg(1), three equivalent Mg(3), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to three equivalent Mg(1), three equivalent Mg(3), and three equivalent Mg(4) atoms. is represented by the CIF card [CIF]
data_Mg9Si5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.964
_cell_length_b   12.964
_cell_length_c   12.964
_cell_angle_alpha   32.156
_cell_angle_beta   32.156
_cell_angle_gamma   32.156
_symmetry_Int_Tables_number   1
_cell_volume   548.509
_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  0.618  0.141  0.907  1.0
  Mg  Mg1  1  0.248  0.500  0.752  1.0
  Mg  Mg2  1  0.141  0.907  0.618  1.0
  Mg  Mg3  1  0.500  0.752  0.248  1.0
  Mg  Mg4  1  0.907  0.618  0.141  1.0
  Mg  Mg5  1  0.752  0.248  0.500  1.0
  Mg  Mg6  1  0.075  0.444  0.643  1.0
  Mg  Mg7  1  0.744  0.256  0.000  1.0
  Mg  Mg8  1  0.444  0.643  0.075  1.0
  Mg  Mg9  1  0.256  0.000  0.744  1.0
  Mg  Mg10  1  0.643  0.075  0.444  1.0
  Mg  Mg11  1  0.000  0.744  0.256  1.0
  Mg  Mg12  1  0.859  0.382  0.093  1.0
  Mg  Mg13  1  0.925  0.357  0.556  1.0
  Mg  Mg14  1  0.382  0.093  0.859  1.0
  Mg  Mg15  1  0.357  0.556  0.925  1.0
  Mg  Mg16  1  0.093  0.859  0.382  1.0
  Mg  Mg17  1  0.556  0.925  0.357  1.0
  Si  Si18  1  0.331  0.331  0.331  1.0
  Si  Si19  1  0.442  0.442  0.442  1.0
  Si  Si20  1  0.168  0.168  0.168  1.0
  Si  Si21  1  0.236  0.236  0.236  1.0
  Si  Si22  1  0.056  0.056  0.056  1.0
  Si  Si23  1  0.558  0.558  0.558  1.0
  Si  Si24  1  0.669  0.669  0.669  1.0
  Si  Si25  1  0.944  0.944  0.944  1.0
  Si  Si26  1  0.832  0.832  0.832  1.0
  Si  Si27  1  0.764  0.764  0.764  1.0
[/CIF]
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The crystal structure described by Mg9Si5 crystallizes in the trigonal R32 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Si(2), one Si(3), one Si(4), and one Si(5) atom to form a mixture of distorted corner and edge-sharing MgSi4 tetrahedra. In the second Mg site, Mg(2) is bonded to two equivalent Si(2) and two equivalent Si(3) atoms to form a mixture of distorted corner and edge-sharing MgSi4 tetrahedra. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Si(2), one Si(4), one Si(5), and two equivalent Si(1) atoms. In the fourth Mg site, Mg(4) is bonded to two equivalent Si(1) and two equivalent Si(5) atoms to form a mixture of distorted corner and edge-sharing MgSi4 tetrahedra. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Mg(4) and six equivalent Mg(3) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), and three equivalent Mg(3) atoms. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to three equivalent Mg(1), three equivalent Mg(2), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to three equivalent Mg(1), three equivalent Mg(3), and one Si(3) atom. In the fifth Si site, Si(5) is bonded in a 9-coordinate geometry to three equivalent Mg(1), three equivalent Mg(3), and three equivalent Mg(4) atoms. is represented by the CIF card [CIF]
data_Mg9Si5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   12.964
_cell_length_b   12.964
_cell_length_c   12.964
_cell_angle_alpha   32.156
_cell_angle_beta   32.156
_cell_angle_gamma   32.156
_symmetry_Int_Tables_number   1
_cell_volume   548.509
_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  0.618  0.141  0.907  1.0
  Mg  Mg1  1  0.248  0.500  0.752  1.0
  Mg  Mg2  1  0.141  0.907  0.618  1.0
  Mg  Mg3  1  0.500  0.752  0.248  1.0
  Mg  Mg4  1  0.907  0.618  0.141  1.0
  Mg  Mg5  1  0.752  0.248  0.500  1.0
  Mg  Mg6  1  0.075  0.444  0.643  1.0
  Mg  Mg7  1  0.744  0.256  0.000  1.0
  Mg  Mg8  1  0.444  0.643  0.075  1.0
  Mg  Mg9  1  0.256  0.000  0.744  1.0
  Mg  Mg10  1  0.643  0.075  0.444  1.0
  Mg  Mg11  1  0.000  0.744  0.256  1.0
  Mg  Mg12  1  0.859  0.382  0.093  1.0
  Mg  Mg13  1  0.925  0.357  0.556  1.0
  Mg  Mg14  1  0.382  0.093  0.859  1.0
  Mg  Mg15  1  0.357  0.556  0.925  1.0
  Mg  Mg16  1  0.093  0.859  0.382  1.0
  Mg  Mg17  1  0.556  0.925  0.357  1.0
  Si  Si18  1  0.331  0.331  0.331  1.0
  Si  Si19  1  0.442  0.442  0.442  1.0
  Si  Si20  1  0.168  0.168  0.168  1.0
  Si  Si21  1  0.236  0.236  0.236  1.0
  Si  Si22  1  0.056  0.056  0.056  1.0
  Si  Si23  1  0.558  0.558  0.558  1.0
  Si  Si24  1  0.669  0.669  0.669  1.0
  Si  Si25  1  0.944  0.944  0.944  1.0
  Si  Si26  1  0.832  0.832  0.832  1.0
  Si  Si27  1  0.764  0.764  0.764  1.0
[/CIF]
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