The material structure described by Si crystallizes in the triclinic P1 space group. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to one Si(2), one Si(3), one Si(5), and two equivalent Si(8) atoms. In the second Si site, Si(2) is bonded in a 4-coordinate geometry to one Si(1), one Si(3), one Si(5), and one Si(8) atom. In the third Si site, Si(3) is bonded in a distorted trigonal planar geometry to one Si(1), one Si(2), and one Si(7) atom. In the fourth Si site, Si(4) is bonded in a 4-coordinate geometry to one Si(5), one Si(6), and two equivalent Si(7) atoms. In the fifth Si site, Si(5) is bonded in a 1-coordinate geometry to one Si(1), one Si(2), one Si(4), one Si(8), and two equivalent Si(6) atoms. In the sixth Si site, Si(6) is bonded in a 4-coordinate geometry to one Si(4), one Si(7), and two equivalent Si(5) atoms. In the seventh Si site, Si(7) is bonded in a 1-coordinate geometry to one Si(3), one Si(6), and two equivalent Si(4) atoms. In the eighth Si site, Si(8) is bonded in a 4-coordinate geometry to one Si(2), one Si(5), and two equivalent Si(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.975
_cell_length_b   5.455
_cell_length_c   9.015
_cell_angle_alpha   106.173
_cell_angle_beta   89.297
_cell_angle_gamma   111.239
_symmetry_Int_Tables_number   1
_cell_volume   174.108
_cell_formula_units_Z   8
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  0.095  0.828  0.918  1.0
  Si  Si1  1  0.001  0.211  0.940  1.0
  Si  Si2  1  0.567  0.004  0.759  1.0
  Si  Si3  1  0.126  0.362  0.372  1.0
  Si  Si4  1  0.841  0.070  0.198  1.0
  Si  Si5  1  0.287  0.842  0.318  1.0
  Si  Si6  1  0.568  0.133  0.489  1.0
  Si  Si7  1  0.509  0.566  1.000  1.0
[/CIF]
.
The material structure described by Si crystallizes in the triclinic P1 space group. There are eight inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to one Si(2), one Si(3), one Si(5), and two equivalent Si(8) atoms. In the second Si site, Si(2) is bonded in a 4-coordinate geometry to one Si(1), one Si(3), one Si(5), and one Si(8) atom. In the third Si site, Si(3) is bonded in a distorted trigonal planar geometry to one Si(1), one Si(2), and one Si(7) atom. In the fourth Si site, Si(4) is bonded in a 4-coordinate geometry to one Si(5), one Si(6), and two equivalent Si(7) atoms. In the fifth Si site, Si(5) is bonded in a 1-coordinate geometry to one Si(1), one Si(2), one Si(4), one Si(8), and two equivalent Si(6) atoms. In the sixth Si site, Si(6) is bonded in a 4-coordinate geometry to one Si(4), one Si(7), and two equivalent Si(5) atoms. In the seventh Si site, Si(7) is bonded in a 1-coordinate geometry to one Si(3), one Si(6), and two equivalent Si(4) atoms. In the eighth Si site, Si(8) is bonded in a 4-coordinate geometry to one Si(2), one Si(5), and two equivalent Si(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.975
_cell_length_b   5.455
_cell_length_c   9.015
_cell_angle_alpha   106.173
_cell_angle_beta   89.297
_cell_angle_gamma   111.239
_symmetry_Int_Tables_number   1
_cell_volume   174.108
_cell_formula_units_Z   8
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  0.095  0.828  0.918  1.0
  Si  Si1  1  0.001  0.211  0.940  1.0
  Si  Si2  1  0.567  0.004  0.759  1.0
  Si  Si3  1  0.126  0.362  0.372  1.0
  Si  Si4  1  0.841  0.070  0.198  1.0
  Si  Si5  1  0.287  0.842  0.318  1.0
  Si  Si6  1  0.568  0.133  0.489  1.0
  Si  Si7  1  0.509  0.566  1.000  1.0
[/CIF]
.