data_AlC3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.67
_cell_length_b   3.67
_cell_length_c   3.67
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   AlC3
_chemical_formula_sum   'Al1 C3'
_cell_volume   34.84
_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
  Al  Al0  1  0.59  0.59  0.59  1.0
  C  C1  1  0.89  0.89  0.89  1.0
  C  C2  1  0.0  0.0  0.0  1.0
  C  C3  1  0.3  0.3  0.3  1.0

data_AlC3
_symmetry_space_group_name_H-M   R3m
_cell_length_a   3.67
_cell_length_b   3.67
_cell_length_c   8.98
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   AlC3
_chemical_formula_sum   'Al3 C9'
_cell_volume   104.53
_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
  Al  Al0  3  0.0  0.0  0.41  1.0
  C  C1  3  0.0  0.0  0.0  1.0
  C  C2  3  0.0  0.0  0.11  1.0
  C  C3  3  0.0  0.0  0.7  1.0

Al C C C
AlC3 crystallizes in the trigonal R3m space group. Al(1) is bonded in a 11-coordinate geometry to three equivalent C(2), four equivalent C(1), and four equivalent C(3) atoms. All Al(1)-C(2) bond lengths are 2.22 Å. There are three shorter (2.14 Å) and one longer (2.66 Å) Al(1)-C(1) bond length. There are three shorter (2.14 Å) and one longer (2.66 Å) Al(1)-C(3) bond length. There are three inequivalent C sites. In the first C site, C(1) is bonded in a distorted single-bond geometry to four equivalent Al(1) and one C(2) atom. The C(1)-C(2) bond length is 1.00 Å. In the second C site, C(2) is bonded in a single-bond geometry to three equivalent Al(1) and one C(1) atom. In the third C site, C(3) is bonded in a distorted trigonal planar geometry to four equivalent Al(1) atoms.