data_Na2CuSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.06
_cell_length_b   5.06
_cell_length_c   5.06
_cell_angle_alpha   125.84
_cell_angle_beta   125.84
_cell_angle_gamma   80.16
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2CuSe
_chemical_formula_sum   'Na2 Cu1 Se1'
_cell_volume   82.34
_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  Na1  1  0.0  0.31  0.94  1.0
  Na  Na2  1  0.31  0.0  0.94  1.0
  Cu  Cu0  1  0.0  0.0  0.0  1.0
  Se  Se3  1  0.0  0.0  0.87  1.0

data_Na2CuSe
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.52
_cell_length_b   6.52
_cell_length_c   5.06
_cell_angle_alpha   90.0
_cell_angle_beta   130.08
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Na2CuSe
_chemical_formula_sum   'Na4 Cu2 Se2'
_cell_volume   164.68
_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  4  0.35  0.35  0.63  1.0
  Cu  Cu1  2  0.0  0.0  0.0  1.0
  Se  Se2  2  0.0  0.0  0.87  1.0

Na Na Cu Se
Na Na Cu Se 0 3 o o o 1 3 o o o 2 3 o o - 
Na2CuSe is Copper structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two Na2CuSe clusters. Na(1) is bonded in a single-bond geometry to one Se(1) atom. The Na(1)-Se(1) bond length is 1.38 Å. Cu(1) is bonded in a single-bond geometry to one Se(1) atom. The Cu(1)-Se(1) bond length is 0.64 Å. Se(1) is bonded in a trigonal non-coplanar geometry to two equivalent Na(1) and one Cu(1) atom.