data_NaNiSe2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.93
_cell_length_b   4.93
_cell_length_c   2.86
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NaNiSe2
_chemical_formula_sum   'Na1 Ni1 Se2'
_cell_volume   69.63
_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
  Ni  Ni1  1  0.47  0.47  0.0  1.0
  Se  Se2  1  0.47  0.0  0.43  1.0
  Se  Se3  1  0.0  0.47  0.43  1.0

data_NaNiSe2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.98
_cell_length_b   6.98
_cell_length_c   2.86
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   NaNiSe2
_chemical_formula_sum   'Na2 Ni2 Se4'
_cell_volume   139.26
_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
  Ni  Ni1  2  0.47  0.0  -0.0  1.0
  Se  Se2  4  0.23  0.23  0.43  1.0

Na Ni Se Se
Na Ni Se Se 0 2 - o - 0 2 - o o 0 2 o o - 0 2 o o o 0 3 o - - 0 3 o - o 0 3 o o - 0 3 o o o 0 0 o o + 0 1 o o o 1 3 o o - 1 3 o o o 1 3 + o - 1 3 + o o 1 2 o o - 1 2 o o o 1 2 o + - 1 2 o + o 1 1 o o + 2 3 o o o 2 2 o o + 3 3 o o + 
NaNiSe2 crystallizes in the monoclinic Cm space group. Na(1) is bonded in a 8-coordinate geometry to eight equivalent Se(1) atoms. There are a spread of Na(1)-Se(1) bond distances ranging from 2.61-3.09 Å. Ni(1) is bonded in a 6-coordinate geometry to eight equivalent Se(1) atoms. There are a spread of Ni(1)-Se(1) bond distances ranging from 2.61-3.09 Å. Se(1) is bonded in a 10-coordinate geometry to four equivalent Na(1), four equivalent Ni(1), and two equivalent Se(1) atoms. Both Se(1)-Se(1) bond lengths are 2.86 Å.