data_HfCuSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.47
_cell_length_b   4.47
_cell_length_c   4.47
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HfCuSi2
_chemical_formula_sum   'Hf1 Cu1 Si2'
_cell_volume   63.31
_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  0.58  0.58  0.58  1.0
  Cu  Cu0  1  0.16  0.16  0.16  1.0
  Si  Si2  1  0.0  0.0  0.0  1.0
  Si  Si3  1  0.75  0.75  0.75  1.0

data_HfCuSi2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.47
_cell_length_b   4.47
_cell_length_c   10.96
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   HfCuSi2
_chemical_formula_sum   'Hf3 Cu3 Si6'
_cell_volume   189.94
_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  0.42  1.0
  Si  Si1  3  0.0  0.0  0.0  1.0
  Si  Si2  3  0.0  0.0  0.25  1.0
  Cu  Cu3  3  0.0  0.0  0.84  1.0

Hf Cu Si Si
HfCuSi2 crystallizes in the trigonal R3m space group. Hf(1) is bonded in a distorted single-bond geometry to three equivalent Cu(1), one Si(2), and three equivalent Si(1) atoms. All Hf(1)-Cu(1) bond lengths are 2.75 Å. The Hf(1)-Si(2) bond length is 1.79 Å. All Hf(1)-Si(1) bond lengths are 2.75 Å. Cu(1) is bonded to three equivalent Hf(1) and one Si(1) atom to form distorted CuHf3Si tetrahedra that share corners with three equivalent Si(1)Hf3Cu tetrahedra, corners with six equivalent Cu(1)Hf3Si tetrahedra, and edges with three equivalent Si(1)Hf3Cu tetrahedra. The Cu(1)-Si(1) bond length is 1.79 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to three equivalent Hf(1) and one Cu(1) atom to form distorted SiHf3Cu tetrahedra that share corners with three equivalent Cu(1)Hf3Si tetrahedra, corners with six equivalent Si(1)Hf3Cu tetrahedra, and edges with three equivalent Cu(1)Hf3Si tetrahedra. In the second Si site, Si(2) is bonded in a single-bond geometry to one Hf(1) atom.