data_Na(WSe)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.54
_cell_length_b   5.54
_cell_length_c   5.54
_cell_angle_alpha   127.85
_cell_angle_beta   127.85
_cell_angle_gamma   76.87
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na(WSe)2
_chemical_formula_sum   'Na1 W2 Se2'
_cell_volume   103.15
_cell_formula_units_Z   1
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
  Na  Na0  1  0.0  0.0  0.0  1.0
  W  W3  1  0.0  0.0  0.49  1.0
  W  W4  1  0.0  0.0  0.2  1.0
  Se  Se1  1  0.0  0.44  0.17  1.0
  Se  Se2  1  0.44  0.0  0.17  1.0

data_Na(WSe)2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.89
_cell_length_b   6.89
_cell_length_c   5.54
_cell_angle_alpha   90.0
_cell_angle_beta   128.43
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Na(WSe)2
_chemical_formula_sum   'Na2 W4 Se4'
_cell_volume   206.29
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  Na  Na0  2  0.0  0.0  0.0  1.0
  W  W1  2  0.0  0.0  0.2  1.0
  W  W2  2  0.0  0.0  0.49  1.0
  Se  Se3  4  0.28  0.28  0.73  1.0

Na W W Se Se
Na(WSe)2 crystallizes in the monoclinic Cm space group. Na(1) is bonded in a 3-coordinate geometry to one W(1), one W(2), and two equivalent Se(1) atoms. The Na(1)-W(1) bond length is 2.84 Å. The Na(1)-W(2) bond length is 1.09 Å. Both Na(1)-Se(1) bond lengths are 1.99 Å. There are two inequivalent W sites. In the first W site, W(1) is bonded in a 6-coordinate geometry to one Na(1), one W(2), and four equivalent Se(1) atoms. The W(1)-W(2) bond length is 1.61 Å. There are two shorter (2.47 Å) and two longer (2.99 Å) W(1)-Se(1) bond lengths. In the second W site, W(2) is bonded in a single-bond geometry to one Na(1) and one W(1) atom. Se(1) is bonded in a distorted single-bond geometry to one Na(1) and two equivalent W(1) atoms.