data_FeSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.45
_cell_length_b   4.45
_cell_length_c   4.45
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   FeSi
_chemical_formula_sum   'Fe4 Si4'
_cell_volume   88.13
_cell_formula_units_Z   4
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
  Fe  Fe0  1  0.84  0.83  0.62  1.0
  Fe  Fe1  1  0.83  0.62  0.84  1.0
  Fe  Fe2  1  0.62  0.84  0.83  1.0
  Fe  Fe3  1  0.61  0.61  0.61  1.0
  Si  Si4  1  0.71  0.52  0.93  1.0
  Si  Si5  1  0.52  0.93  0.71  1.0
  Si  Si6  1  0.93  0.71  0.52  1.0
  Si  Si7  1  0.74  0.74  0.74  1.0

data_FeSi
_symmetry_space_group_name_H-M   R3
_cell_length_a   6.29
_cell_length_b   6.29
_cell_length_c   7.71
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   146
_chemical_formula_structural   FeSi
_chemical_formula_sum   'Fe12 Si12'
_cell_volume   264.4
_cell_formula_units_Z   12
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  'x+1/3, y+2/3, z+2/3'
  5  '-y+1/3, x-y+2/3, z+2/3'
  6  '-x+y+1/3, -x+2/3, z+2/3'
  7  'x+2/3, y+1/3, z+1/3'
  8  '-y+2/3, x-y+1/3, z+1/3'
  9  '-x+y+2/3, -x+1/3, z+1/3'
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
  Fe  Fe0  9  0.07  0.92  0.76  1.0
  Fe  Fe1  3  0.0  0.0  0.61  1.0
  Si  Si2  9  0.13  0.68  0.39  1.0
  Si  Si3  3  0.0  0.0  0.74  1.0

Fe Fe Fe Fe Si Si Si Si
Fe Fe Fe Fe Si Si Si Si 0 7 o o o 0 6 o o o 1 4 o o o 1 7 o o o 2 5 o o o 2 7 o o o 3 7 o o o 
FeSi is alpha Po structured and crystallizes in the trigonal R3 space group. The structure is zero-dimensional and consists of three FeSi clusters. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted water-like geometry to one Si(1) and one Si(2) atom. The Fe(1)-Si(1) bond length is 0.82 Å. The Fe(1)-Si(2) bond length is 0.82 Å. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Si(2) atom. The Fe(2)-Si(2) bond length is 1.04 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a single-bond geometry to one Fe(1) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one Fe(2) and three equivalent Fe(1) atoms.