data_KCuSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.8
_cell_length_b   4.8
_cell_length_c   4.8
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   KCuSe
_chemical_formula_sum   'K1 Cu1 Se1'
_cell_volume   78.37
_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
  K  K1  1  0.0  0.0  0.0  1.0
  Cu  Cu0  1  0.4  0.4  0.4  1.0
  Se  Se2  1  0.7  0.7  0.7  1.0

data_KCuSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.8
_cell_length_b   4.8
_cell_length_c   11.77
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   KCuSe
_chemical_formula_sum   'K3 Cu3 Se3'
_cell_volume   235.11
_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
  K  K0  3  0.0  0.0  0.0  1.0
  Cu  Cu1  3  0.0  0.0  0.6  1.0
  Se  Se2  3  0.0  0.0  0.3  1.0

K Cu Se
K Cu Se 0 2 - - o 0 2 - o - 0 2 o - - 0 1 - o o 0 1 o - o 0 1 o o - 1 2 - o o 1 2 o - o 1 2 o o - 
KCuSe is half-Heusler structured and crystallizes in the trigonal R3m space group. K(1) is bonded to three equivalent Cu(1) and four equivalent Se(1) atoms to form distorted KCu3Se4 hexagonal pyramids that share corners with three equivalent Se(1)K4Cu3 hexagonal pyramids, corners with six equivalent K(1)Cu3Se4 hexagonal pyramids, edges with three equivalent Se(1)K4Cu3 hexagonal pyramids, and edges with six equivalent K(1)Cu3Se4 hexagonal pyramids. All K(1)-Cu(1) bond lengths are 2.87 Å. There are three shorter (2.80 Å) and one longer (3.55 Å) K(1)-Se(1) bond length. Cu(1) is bonded in a hexagonal planar geometry to three equivalent K(1) and three equivalent Se(1) atoms. All Cu(1)-Se(1) bond lengths are 2.80 Å. Se(1) is bonded to four equivalent K(1) and three equivalent Cu(1) atoms to form SeK4Cu3 hexagonal pyramids that share corners with three equivalent K(1)Cu3Se4 hexagonal pyramids, corners with six equivalent Se(1)K4Cu3 hexagonal pyramids, edges with three equivalent K(1)Cu3Se4 hexagonal pyramids, and edges with six equivalent Se(1)K4Cu3 hexagonal pyramids.