data_CaHgAs
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.93
_cell_length_b   4.93
_cell_length_c   4.93
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaHgAs
_chemical_formula_sum   'Ca1 Hg1 As1'
_cell_volume   84.86
_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
  Ca  Ca1  1  0.0  0.0  0.0  1.0
  Hg  Hg2  1  0.23  0.23  0.23  1.0
  As  As0  1  0.74  0.74  0.74  1.0

data_CaHgAs
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.93
_cell_length_b   4.93
_cell_length_c   12.08
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   CaHgAs
_chemical_formula_sum   'Ca3 Hg3 As3'
_cell_volume   254.57
_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
  Ca  Ca0  3  0.0  0.0  0.0  1.0
  Hg  Hg1  3  0.0  0.0  0.77  1.0
  As  As2  3  0.0  0.0  0.26  1.0

Ca Hg As
CaHgAs is half-Heusler structured and crystallizes in the trigonal R3m space group. Ca(1) is bonded in a body-centered cubic geometry to four equivalent Hg(1) and four equivalent As(1) atoms. There is one shorter (2.80 Å) and three longer (3.10 Å) Ca(1)-Hg(1) bond lengths. There are three shorter (3.00 Å) and one longer (3.09 Å) Ca(1)-As(1) bond length. Hg(1) is bonded to four equivalent Ca(1) atoms to form HgCa4 tetrahedra that share corners with four equivalent As(1)Ca4 tetrahedra, corners with twelve equivalent Hg(1)Ca4 tetrahedra, and edges with six equivalent As(1)Ca4 tetrahedra. As(1) is bonded to four equivalent Ca(1) atoms to form AsCa4 tetrahedra that share corners with four equivalent Hg(1)Ca4 tetrahedra, corners with twelve equivalent As(1)Ca4 tetrahedra, and edges with six equivalent Hg(1)Ca4 tetrahedra.