data_CuNiSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.25
_cell_length_b   3.25
_cell_length_c   6.73
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CuNiSe2
_chemical_formula_sum   'Cu1 Ni1 Se2'
_cell_volume   71.24
_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
  Cu  Cu0  1  0.63  0.63  0.48  1.0
  Ni  Ni1  1  0.0  0.0  0.98  1.0
  Se  Se2  1  0.63  0.63  0.94  1.0
  Se  Se3  1  0.0  0.0  0.43  1.0

data_CuNiSe2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.6
_cell_length_b   4.6
_cell_length_c   6.73
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   CuNiSe2
_chemical_formula_sum   'Cu2 Ni2 Se4'
_cell_volume   142.47
_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
  Cu  Cu0  2  0.13  0.5  0.48  1.0
  Ni  Ni1  2  0.0  0.0  0.98  1.0
  Se  Se2  2  0.0  0.0  0.43  1.0
  Se  Se3  2  0.13  0.5  0.94  1.0

Cu Ni Se Se
NiCuSe2 crystallizes in the monoclinic Cm space group. Ni(1) is bonded in a 5-coordinate geometry to one Se(2) and four equivalent Se(1) atoms. The Ni(1)-Se(2) bond length is 2.99 Å. There are a spread of Ni(1)-Se(1) bond distances ranging from 1.74-2.90 Å. Cu(1) is bonded in a 5-coordinate geometry to one Se(1) and four equivalent Se(2) atoms. The Cu(1)-Se(1) bond length is 3.04 Å. There are a spread of Cu(1)-Se(2) bond distances ranging from 1.76-2.91 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to four equivalent Ni(1) and one Cu(1) atom. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Ni(1) and four equivalent Cu(1) atoms.