data_CaAs4Se
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.82
_cell_length_b   5.82
_cell_length_c   5.82
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaAs4Se
_chemical_formula_sum   'Ca1 As4 Se1'
_cell_volume   139.05
_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  Ca4  1  0.0  0.0  0.0  1.0
  As  As0  1  0.21  0.21  0.01  1.0
  As  As1  1  0.21  0.01  0.21  1.0
  As  As2  1  0.01  0.21  0.21  1.0
  As  As3  1  0.01  0.01  0.01  1.0
  Se  Se5  1  0.06  0.06  0.06  1.0

data_CaAs4Se
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.82
_cell_length_b   5.82
_cell_length_c   14.24
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   CaAs4Se
_chemical_formula_sum   'Ca3 As12 Se3'
_cell_volume   417.14
_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
  As  As1  9  0.13  0.07  0.85  1.0
  As  As2  3  0.0  0.0  0.99  1.0
  Se  Se3  3  0.0  0.0  0.94  1.0

Ca As As As As Se
Ca As As As As Se 0 4 o o o 1 2 o o o 1 3 o o o 2 3 o o o 4 5 o o o 
CaAs4Se is Copper structured and crystallizes in the trigonal R3m space group. The structure is zero-dimensional and consists of three CaAs4Se clusters. Ca(1) is bonded in a single-bond geometry to one As(2) atom. The Ca(1)-As(2) bond length is 0.18 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 3-coordinate geometry to two equivalent As(1) and one Se(1) atom. Both As(1)-As(1) bond lengths are 1.16 Å. The As(1)-Se(1) bond length is 1.43 Å. In the second As site, As(2) is bonded in a linear geometry to one Ca(1) and one Se(1) atom. The As(2)-Se(1) bond length is 0.62 Å. Se(1) is bonded in a distorted single-bond geometry to one As(2) and three equivalent As(1) atoms.