The structure described by Si crystallizes in the cubic Fd-3m space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to four equivalent Si(2) atoms. In the second Si site, Si(2) is bonded to one Si(1) and three equivalent Si(3) atoms to form corner-sharing SiSi4 tetrahedra. In the third Si site, Si(3) is bonded in a distorted see-saw-like geometry to one Si(2) and three equivalent Si(3) atoms. is represented by the CIF card [CIF]
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.378
_cell_length_b   10.378
_cell_length_c   10.378
_cell_angle_alpha   60.000
_cell_angle_beta   60.000
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   790.431
_cell_formula_units_Z   34
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
  Si  Si0  1  0.500  0.500  0.500  1.0
  Si  Si1  1  0.750  0.750  0.750  1.0
  Si  Si2  1  0.389  0.389  0.389  1.0
  Si  Si3  1  0.418  0.861  0.861  1.0
  Si  Si4  1  0.861  0.418  0.861  1.0
  Si  Si5  1  0.861  0.861  0.418  1.0
  Si  Si6  1  0.389  0.832  0.389  1.0
  Si  Si7  1  0.389  0.389  0.832  1.0
  Si  Si8  1  0.832  0.389  0.389  1.0
  Si  Si9  1  0.861  0.861  0.861  1.0
  Si  Si10  1  0.364  0.753  0.753  1.0
  Si  Si11  1  0.121  0.497  0.886  1.0
  Si  Si12  1  0.497  0.121  0.497  1.0
  Si  Si13  1  0.497  0.497  0.121  1.0
  Si  Si14  1  0.121  0.886  0.497  1.0
  Si  Si15  1  0.497  0.886  0.121  1.0
  Si  Si16  1  0.497  0.121  0.886  1.0
  Si  Si17  1  0.753  0.364  0.753  1.0
  Si  Si18  1  0.753  0.753  0.364  1.0
  Si  Si19  1  0.364  0.129  0.753  1.0
  Si  Si20  1  0.364  0.753  0.129  1.0
  Si  Si21  1  0.753  0.129  0.753  1.0
  Si  Si22  1  0.129  0.364  0.753  1.0
  Si  Si23  1  0.129  0.753  0.364  1.0
  Si  Si24  1  0.753  0.753  0.129  1.0
  Si  Si25  1  0.886  0.121  0.497  1.0
  Si  Si26  1  0.886  0.497  0.121  1.0
  Si  Si27  1  0.121  0.497  0.497  1.0
  Si  Si28  1  0.886  0.497  0.497  1.0
  Si  Si29  1  0.497  0.886  0.497  1.0
  Si  Si30  1  0.497  0.497  0.886  1.0
  Si  Si31  1  0.753  0.364  0.129  1.0
  Si  Si32  1  0.753  0.129  0.364  1.0
  Si  Si33  1  0.129  0.753  0.753  1.0
[/CIF]
.
The structure described by Si crystallizes in the cubic Fd-3m space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to four equivalent Si(2) atoms. In the second Si site, Si(2) is bonded to one Si(1) and three equivalent Si(3) atoms to form corner-sharing SiSi4 tetrahedra. In the third Si site, Si(3) is bonded in a distorted see-saw-like geometry to one Si(2) and three equivalent Si(3) atoms. is represented by the CIF card [CIF]
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.378
_cell_length_b   10.378
_cell_length_c   10.378
_cell_angle_alpha   60.000
_cell_angle_beta   60.000
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   790.431
_cell_formula_units_Z   34
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
  Si  Si0  1  0.500  0.500  0.500  1.0
  Si  Si1  1  0.750  0.750  0.750  1.0
  Si  Si2  1  0.389  0.389  0.389  1.0
  Si  Si3  1  0.418  0.861  0.861  1.0
  Si  Si4  1  0.861  0.418  0.861  1.0
  Si  Si5  1  0.861  0.861  0.418  1.0
  Si  Si6  1  0.389  0.832  0.389  1.0
  Si  Si7  1  0.389  0.389  0.832  1.0
  Si  Si8  1  0.832  0.389  0.389  1.0
  Si  Si9  1  0.861  0.861  0.861  1.0
  Si  Si10  1  0.364  0.753  0.753  1.0
  Si  Si11  1  0.121  0.497  0.886  1.0
  Si  Si12  1  0.497  0.121  0.497  1.0
  Si  Si13  1  0.497  0.497  0.121  1.0
  Si  Si14  1  0.121  0.886  0.497  1.0
  Si  Si15  1  0.497  0.886  0.121  1.0
  Si  Si16  1  0.497  0.121  0.886  1.0
  Si  Si17  1  0.753  0.364  0.753  1.0
  Si  Si18  1  0.753  0.753  0.364  1.0
  Si  Si19  1  0.364  0.129  0.753  1.0
  Si  Si20  1  0.364  0.753  0.129  1.0
  Si  Si21  1  0.753  0.129  0.753  1.0
  Si  Si22  1  0.129  0.364  0.753  1.0
  Si  Si23  1  0.129  0.753  0.364  1.0
  Si  Si24  1  0.753  0.753  0.129  1.0
  Si  Si25  1  0.886  0.121  0.497  1.0
  Si  Si26  1  0.886  0.497  0.121  1.0
  Si  Si27  1  0.121  0.497  0.497  1.0
  Si  Si28  1  0.886  0.497  0.497  1.0
  Si  Si29  1  0.497  0.886  0.497  1.0
  Si  Si30  1  0.497  0.497  0.886  1.0
  Si  Si31  1  0.753  0.364  0.129  1.0
  Si  Si32  1  0.753  0.129  0.364  1.0
  Si  Si33  1  0.129  0.753  0.753  1.0
[/CIF]
.