data_HfTaCu
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.5
_cell_length_b   4.5
_cell_length_c   4.5
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HfTaCu
_chemical_formula_sum   'Hf1 Ta1 Cu1'
_cell_volume   64.38
_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
  Hf  Hf1  1  0.77  0.77  0.77  1.0
  Ta  Ta2  1  0.18  0.18  0.18  1.0
  Cu  Cu0  1  0.0  0.0  0.0  1.0

data_HfTaCu
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.5
_cell_length_b   4.5
_cell_length_c   11.02
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   HfTaCu
_chemical_formula_sum   'Hf3 Ta3 Cu3'
_cell_volume   193.13
_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
  Hf  Hf0  3  0.0  0.0  0.23  1.0
  Ta  Ta1  3  0.0  0.0  0.82  1.0
  Cu  Cu2  3  0.0  0.0  1.0  1.0

Hf Ta Cu
Hf Ta Cu 0 2 + o + 0 2 o + + 0 2 + + o 0 2 + + + 0 1 o + + 0 1 + o + 0 1 + + o 1 2 o o o 
HfTaCu is half-Heusler structured and crystallizes in the trigonal R3m space group. Hf(1) is bonded in a 7-coordinate geometry to three equivalent Ta(1) and four equivalent Cu(1) atoms. All Hf(1)-Ta(1) bond lengths are 2.73 Å. There is one shorter (2.52 Å) and three longer (2.84 Å) Hf(1)-Cu(1) bond lengths. Ta(1) is bonded in a distorted single-bond geometry to three equivalent Hf(1) and four equivalent Cu(1) atoms. There is one shorter (1.99 Å) and three longer (3.09 Å) Ta(1)-Cu(1) bond lengths. Cu(1) is bonded in a 8-coordinate geometry to four equivalent Hf(1) and four equivalent Ta(1) atoms.