data_BaC2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.14
_cell_length_b   5.14
_cell_length_c   5.14
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   BaC2
_chemical_formula_sum   'Ba2 C4'
_cell_volume   96.0
_cell_formula_units_Z   2
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
  Ba  Ba0  1  0.0  0.0  0.0  1.0
  Ba  Ba1  1  0.82  0.82  0.82  1.0
  C  C2  1  0.73  0.73  0.54  1.0
  C  C3  1  0.54  0.73  0.73  1.0
  C  C4  1  0.73  0.54  0.73  1.0
  C  C5  1  0.54  0.54  0.54  1.0

data_BaC2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.14
_cell_length_b   5.14
_cell_length_c   12.59
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   BaC2
_chemical_formula_sum   'Ba6 C12'
_cell_volume   288.0
_cell_formula_units_Z   6
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
  Ba  Ba0  3  0.0  0.0  0.0  1.0
  Ba  Ba1  3  0.0  0.0  0.18  1.0
  C  C2  9  0.12  0.06  0.34  1.0
  C  C3  3  0.0  0.0  0.46  1.0

Ba Ba C C C C
BaC2 crystallizes in the trigonal R3m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a distorted trigonal planar geometry to one Ba(2) and three equivalent C(1) atoms. The Ba(1)-Ba(2) bond length is 2.30 Å. All Ba(1)-C(1) bond lengths are 2.42 Å. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one Ba(1), three equivalent C(1), and three equivalent C(2) atoms. All Ba(2)-C(1) bond lengths are 1.99 Å. All Ba(2)-C(2) bond lengths are 3.06 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one C(2), and two equivalent C(1) atoms. The C(1)-C(2) bond length is 1.63 Å. Both C(1)-C(1) bond lengths are 0.94 Å. In the second C site, C(2) is bonded in a 6-coordinate geometry to three equivalent Ba(2) and three equivalent C(1) atoms.