data_HfTiSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.53
_cell_length_b   4.53
_cell_length_c   4.53
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HfTiSi2
_chemical_formula_sum   'Hf1 Ti1 Si2'
_cell_volume   65.74
_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  Hf0  1  0.2  0.2  0.2  1.0
  Ti  Ti3  1  0.0  0.0  0.0  1.0
  Si  Si1  1  0.6  0.6  0.6  1.0
  Si  Si2  1  0.8  0.8  0.8  1.0

data_HfTiSi2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.53
_cell_length_b   4.53
_cell_length_c   11.1
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   HfTiSi2
_chemical_formula_sum   'Hf3 Ti3 Si6'
_cell_volume   197.22
_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  0.8  1.0
  Ti  Ti1  3  0.0  0.0  0.0  1.0
  Si  Si2  3  0.0  0.0  0.2  1.0
  Si  Si3  3  0.0  0.0  0.4  1.0

Hf Ti Si Si
HfTiSi2 crystallizes in the trigonal R3m space group. Hf(1) is bonded in a 7-coordinate geometry to one Ti(1), three equivalent Si(1), and three equivalent Si(2) atoms. The Hf(1)-Ti(1) bond length is 2.26 Å. All Hf(1)-Si(1) bond lengths are 2.71 Å. All Hf(1)-Si(2) bond lengths are 2.71 Å. Ti(1) is bonded in a 2-coordinate geometry to one Hf(1), one Si(2), and three equivalent Si(1) atoms. The Ti(1)-Si(2) bond length is 2.16 Å. All Ti(1)-Si(1) bond lengths are 2.71 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to three equivalent Hf(1), three equivalent Ti(1), and one Si(2) atom to form distorted edge-sharing SiHf3Ti3Si hexagonal pyramids. The Si(1)-Si(2) bond length is 2.26 Å. In the second Si site, Si(2) is bonded in a 1-coordinate geometry to three equivalent Hf(1), one Ti(1), and one Si(1) atom.