The material 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(4), one Si(5), and one Si(7) atom. In the second Si site, Si(2) is bonded to one Si(1), one Si(4), one Si(6), one Si(7), and one Si(8) atom to form distorted SiSi5 trigonal bipyramids that share corners with two equivalent Si(6)Si4 tetrahedra, corners with three equivalent Si(3)Si4 tetrahedra, and  a faceface with one Si(4)Si5 trigonal bipyramid. In the third Si site, Si(3) is bonded to one Si(1), one Si(5), one Si(6), and one Si(7) atom to form corner-sharing SiSi4 tetrahedra. In the fourth Si site, Si(4) is bonded to one Si(1), one Si(2), one Si(5), one Si(6), and one Si(8) atom to form distorted SiSi5 trigonal bipyramids that share corners with two equivalent Si(6)Si4 tetrahedra, corners with three equivalent Si(3)Si4 tetrahedra, and  a faceface with one Si(2)Si5 trigonal bipyramid. In the fifth Si site, Si(5) is bonded in a 5-coordinate geometry to one Si(1), one Si(3), one Si(4), one Si(7), and one Si(8) atom. In the sixth Si site, Si(6) is bonded to one Si(2), one Si(3), one Si(4), and one Si(8) atom to form corner-sharing SiSi4 tetrahedra. In the seventh Si site, Si(7) is bonded in a 5-coordinate geometry to one Si(1), one Si(2), one Si(3), one Si(5), and one Si(8) atom. In the eighth Si site, Si(8) is bonded in a 5-coordinate geometry to one Si(2), one Si(4), one Si(5), one Si(6), and one Si(7) atom. is represented by the CIF file [CIF]
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.386
_cell_length_b   4.993
_cell_length_c   6.889
_cell_angle_alpha   69.433
_cell_angle_beta   109.947
_cell_angle_gamma   96.594
_symmetry_Int_Tables_number   1
_cell_volume   163.065
_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  0.977  0.236  0.117  1.0
  Si  Si1  1  0.798  0.556  0.739  1.0
  Si  Si2  1  0.422  0.245  0.310  1.0
  Si  Si3  1  0.790  0.926  0.897  1.0
  Si  Si4  1  0.769  0.550  0.241  1.0
  Si  Si5  1  0.445  0.249  0.654  1.0
  Si  Si6  1  0.780  0.950  0.395  1.0
  Si  Si7  1  0.004  0.255  0.625  1.0
[/CIF]
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The material 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(4), one Si(5), and one Si(7) atom. In the second Si site, Si(2) is bonded to one Si(1), one Si(4), one Si(6), one Si(7), and one Si(8) atom to form distorted SiSi5 trigonal bipyramids that share corners with two equivalent Si(6)Si4 tetrahedra, corners with three equivalent Si(3)Si4 tetrahedra, and  a faceface with one Si(4)Si5 trigonal bipyramid. In the third Si site, Si(3) is bonded to one Si(1), one Si(5), one Si(6), and one Si(7) atom to form corner-sharing SiSi4 tetrahedra. In the fourth Si site, Si(4) is bonded to one Si(1), one Si(2), one Si(5), one Si(6), and one Si(8) atom to form distorted SiSi5 trigonal bipyramids that share corners with two equivalent Si(6)Si4 tetrahedra, corners with three equivalent Si(3)Si4 tetrahedra, and  a faceface with one Si(2)Si5 trigonal bipyramid. In the fifth Si site, Si(5) is bonded in a 5-coordinate geometry to one Si(1), one Si(3), one Si(4), one Si(7), and one Si(8) atom. In the sixth Si site, Si(6) is bonded to one Si(2), one Si(3), one Si(4), and one Si(8) atom to form corner-sharing SiSi4 tetrahedra. In the seventh Si site, Si(7) is bonded in a 5-coordinate geometry to one Si(1), one Si(2), one Si(3), one Si(5), and one Si(8) atom. In the eighth Si site, Si(8) is bonded in a 5-coordinate geometry to one Si(2), one Si(4), one Si(5), one Si(6), and one Si(7) atom. is represented by the CIF file [CIF]
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.386
_cell_length_b   4.993
_cell_length_c   6.889
_cell_angle_alpha   69.433
_cell_angle_beta   109.947
_cell_angle_gamma   96.594
_symmetry_Int_Tables_number   1
_cell_volume   163.065
_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  0.977  0.236  0.117  1.0
  Si  Si1  1  0.798  0.556  0.739  1.0
  Si  Si2  1  0.422  0.245  0.310  1.0
  Si  Si3  1  0.790  0.926  0.897  1.0
  Si  Si4  1  0.769  0.550  0.241  1.0
  Si  Si5  1  0.445  0.249  0.654  1.0
  Si  Si6  1  0.780  0.950  0.395  1.0
  Si  Si7  1  0.004  0.255  0.625  1.0
[/CIF]
.