data_NbCu2Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.0
_cell_length_b   9.0
_cell_length_c   9.0
_cell_angle_alpha   18.39
_cell_angle_beta   18.39
_cell_angle_gamma   18.39
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NbCu2Se
_chemical_formula_sum   'Nb1 Cu2 Se1'
_cell_volume   63.38
_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
  Nb  Nb2  1  0.0  0.0  0.27  1.0
  Cu  Cu0  1  0.0  0.0  0.9  1.0
  Cu  Cu1  1  0.0  0.0  0.63  1.0
  Se  Se3  1  0.0  0.0  0.0  1.0

data_NbCu2Se
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.98
_cell_length_b   2.88
_cell_length_c   9.0
_cell_angle_alpha   90.0
_cell_angle_beta   100.63
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   NbCu2Se
_chemical_formula_sum   'Nb2 Cu4 Se2'
_cell_volume   126.76
_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
  Nb  Nb0  2  0.0  0.0  0.73  1.0
  Cu  Cu1  2  0.0  0.0  0.1  1.0
  Cu  Cu2  2  0.0  0.0  0.37  1.0
  Se  Se3  2  0.0  0.0  0.0  1.0

Nb Cu Cu Se
NbCu2Se crystallizes in the monoclinic Cm space group. Nb(1) is bonded in a distorted single-bond geometry to one Cu(2) and one Se(1) atom. The Nb(1)-Cu(2) bond length is 3.28 Å. The Nb(1)-Se(1) bond length is 2.42 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a single-bond geometry to one Cu(2) and one Se(1) atom. The Cu(1)-Cu(2) bond length is 2.44 Å. The Cu(1)-Se(1) bond length is 0.86 Å. In the second Cu site, Cu(2) is bonded to one Nb(1), one Cu(1), and six equivalent Cu(2) atoms to form a mixture of distorted corner and edge-sharing CuNbCu7 hexagonal bipyramids. All Cu(2)-Cu(2) bond lengths are 2.88 Å. Se(1) is bonded in a single-bond geometry to one Nb(1) and one Cu(1) atom.