data_K2TaSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.25
_cell_length_b   6.25
_cell_length_c   6.25
_cell_angle_alpha   138.23
_cell_angle_beta   138.23
_cell_angle_gamma   60.54
_symmetry_Int_Tables_number   1
_chemical_formula_structural   K2TaSe
_chemical_formula_sum   'K2 Ta1 Se1'
_cell_volume   107.21
_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  K0  1  0.0  0.23  0.7  1.0
  K  K1  1  0.23  0.0  0.7  1.0
  Ta  Ta3  1  0.0  0.0  0.4  1.0
  Se  Se2  1  0.0  0.0  0.0  1.0

data_K2TaSe
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.3
_cell_length_b   6.3
_cell_length_c   6.25
_cell_angle_alpha   90.0
_cell_angle_beta   120.27
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   K2TaSe
_chemical_formula_sum   'K4 Ta2 Se2'
_cell_volume   214.41
_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
  K  K0  4  0.39  0.39  0.47  1.0
  Ta  Ta1  2  0.0  0.0  0.4  1.0
  Se  Se2  2  0.0  0.0  0.0  1.0

K K Ta Se
K2TaSe crystallizes in the monoclinic Cm space group. K(1) is bonded in a distorted single-bond geometry to one Ta(1) and two equivalent Se(1) atoms. The K(1)-Ta(1) bond length is 1.25 Å. There is one shorter (3.09 Å) and one longer (3.64 Å) K(1)-Se(1) bond length. Ta(1) is bonded in a 3-coordinate geometry to two equivalent K(1) and one Se(1) atom. The Ta(1)-Se(1) bond length is 2.49 Å. Se(1) is bonded in a 5-coordinate geometry to four equivalent K(1) and one Ta(1) atom.