data_NaCuSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.42
_cell_length_b   4.42
_cell_length_c   4.42
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NaCuSe
_chemical_formula_sum   'Na1 Cu1 Se1'
_cell_volume   60.97
_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  0.0  0.0  1.0
  Cu  Cu0  1  0.12  0.12  0.12  1.0
  Se  Se2  1  0.69  0.69  0.69  1.0

data_NaCuSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.42
_cell_length_b   4.42
_cell_length_c   10.82
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   NaCuSe
_chemical_formula_sum   'Na3 Cu3 Se3'
_cell_volume   182.92
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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  3  0.0  0.0  0.0  1.0
  Cu  Cu1  3  0.0  0.0  0.88  1.0
  Se  Se2  3  0.0  0.0  0.31  1.0

Na Cu Se
Na Cu Se 0 1 o o o 0 2 o - - 0 2 - o - 0 2 - - o 1 2 o - - 1 2 - o - 1 2 - - o 
NaCuSe is half-Heusler structured and crystallizes in the trigonal R3m space group. Na(1) is bonded in a distorted single-bond geometry to one Cu(1) and four equivalent Se(1) atoms. The Na(1)-Cu(1) bond length is 1.34 Å. There are three shorter (2.56 Å) and one longer (3.40 Å) Na(1)-Se(1) bond length. Cu(1) is bonded in a single-bond geometry to one Na(1) and three equivalent Se(1) atoms. All Cu(1)-Se(1) bond lengths are 2.79 Å. Se(1) is bonded in a distorted trigonal planar geometry to four equivalent Na(1) and three equivalent Cu(1) atoms.