data_CuSiSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.37
_cell_length_b   4.37
_cell_length_c   4.37
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CuSiSe
_chemical_formula_sum   'Cu1 Si1 Se1'
_cell_volume   58.89
_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  0.09  0.09  0.09  1.0
  Si  Si2  1  0.0  0.0  0.0  1.0
  Se  Se1  1  0.54  0.54  0.54  1.0

data_CuSiSe
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.37
_cell_length_b   4.37
_cell_length_c   10.7
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   CuSiSe
_chemical_formula_sum   'Cu3 Si3 Se3'
_cell_volume   176.67
_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
  Si  Si0  3  0.0  0.0  0.0  1.0
  Cu  Cu1  3  0.0  0.0  0.91  1.0
  Se  Se2  3  0.0  0.0  0.46  1.0

Cu Si Se
Cu Si Se 0 1 o o o 0 2 o o - 0 2 o - o 0 2 o - - 0 2 - o o 0 2 - o - 0 2 - - o 1 2 o o - 1 2 o - o 1 2 o - - 1 2 - o o 1 2 - o - 1 2 - - o 
CuSiSe crystallizes in the trigonal R3m space group. Cu(1) is bonded to one Si(1) and three equivalent Se(1) atoms to form distorted CuSiSe3 tetrahedra that share corners with three equivalent Se(1)Cu3Si3 octahedra, corners with three equivalent Si(1)CuSe3 tetrahedra, corners with six equivalent Cu(1)SiSe3 tetrahedra, and edges with three equivalent Si(1)CuSe3 tetrahedra. The corner-sharing octahedral tilt angles are 63°. The Cu(1)-Si(1) bond length is 0.94 Å. All Cu(1)-Se(1) bond lengths are 2.84 Å. Si(1) is bonded to one Cu(1) and three equivalent Se(1) atoms to form distorted SiCuSe3 tetrahedra that share corners with three equivalent Se(1)Cu3Si3 octahedra, corners with three equivalent Cu(1)SiSe3 tetrahedra, corners with six equivalent Si(1)CuSe3 tetrahedra, and edges with three equivalent Cu(1)SiSe3 tetrahedra. The corner-sharing octahedral tilt angles are 63°. All Si(1)-Se(1) bond lengths are 2.84 Å. Se(1) is bonded to three equivalent Cu(1) and three equivalent Si(1) atoms to form SeCu3Si3 octahedra that share corners with three equivalent Cu(1)SiSe3 tetrahedra, corners with three equivalent Si(1)CuSe3 tetrahedra, and edges with six equivalent Se(1)Cu3Si3 octahedra.