data_NbC4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.31
_cell_length_b   6.31
_cell_length_c   6.31
_cell_angle_alpha   109.47
_cell_angle_beta   109.47
_cell_angle_gamma   109.47
_symmetry_Int_Tables_number   1
_chemical_formula_structural   NbC4
_chemical_formula_sum   'Nb4 C16'
_cell_volume   193.4
_cell_formula_units_Z   4
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
  Nb  Nb16  1  0.24  0.24  0.24  1.0
  Nb  Nb17  1  0.59  0.41  0.41  1.0
  Nb  Nb18  1  0.41  0.59  0.41  1.0
  Nb  Nb19  1  0.41  0.41  0.59  1.0
  C  C0  1  0.56  0.56  0.56  1.0
  C  C1  1  0.92  0.08  0.08  1.0
  C  C2  1  0.08  0.92  0.08  1.0
  C  C3  1  0.08  0.08  0.92  1.0
  C  C4  1  0.0  0.0  0.8  1.0
  C  C5  1  0.0  0.0  0.49  1.0
  C  C6  1  0.0  0.8  0.0  1.0
  C  C7  1  0.0  0.49  0.0  1.0
  C  C8  1  0.8  0.0  0.0  1.0
  C  C9  1  0.49  0.0  0.0  1.0
  C  C10  1  0.64  0.0  0.87  1.0
  C  C11  1  0.0  0.64  0.77  1.0
  C  C12  1  0.0  0.87  0.64  1.0
  C  C13  1  0.64  0.77  0.0  1.0
  C  C14  1  0.87  0.64  0.0  1.0
  C  C15  1  0.77  0.0  0.64  1.0

data_NbC4
_symmetry_space_group_name_H-M   R3
_cell_length_a   10.3
_cell_length_b   10.3
_cell_length_c   6.31
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   146
_chemical_formula_structural   NbC4
_chemical_formula_sum   'Nb12 C48'
_cell_volume   580.19
_cell_formula_units_Z   12
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  'x+2/3, y+1/3, z+1/3'
  5  '-y+2/3, x-y+1/3, z+1/3'
  6  '-x+y+2/3, -x+1/3, z+1/3'
  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'
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
  Nb  Nb0  9  0.13  0.06  0.47  1.0
  Nb  Nb1  3  0.0  0.0  0.24  1.0
  C  C2  9  0.03  0.84  0.84  1.0
  C  C3  9  0.05  0.11  0.03  1.0
  C  C4  9  0.07  0.13  0.93  1.0
  C  C5  9  0.17  0.47  0.47  1.0
  C  C6  9  0.17  0.34  0.83  1.0
  C  C7  3  0.0  0.0  0.56  1.0

Nb Nb Nb Nb C C C C C C C C C C C C C C C C
NbC4 crystallizes in the trigonal R3 space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 3-coordinate geometry to three equivalent C(2) atoms. All Nb(1)-C(2) bond lengths are 1.64 Å. In the second Nb site, Nb(2) is bonded in a single-bond geometry to one C(1), one C(4), and one C(6) atom. The Nb(2)-C(1) bond length is 1.27 Å. The Nb(2)-C(4) bond length is 2.62 Å. The Nb(2)-C(6) bond length is 2.31 Å. There are six inequivalent C sites. In the first C site, C(1) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Nb(2) atoms. In the second C site, C(2) is bonded in a 2-coordinate geometry to one Nb(1) and one C(3) atom. The C(2)-C(3) bond length is 0.63 Å. In the third C site, C(3) is bonded in a 3-coordinate geometry to one C(2), one C(5), and one C(6) atom. The C(3)-C(5) bond length is 1.06 Å. The C(3)-C(6) bond length is 1.44 Å. In the fourth C site, C(4) is bonded in a 3-coordinate geometry to one Nb(2), one C(5), and one C(6) atom. The C(4)-C(5) bond length is 1.49 Å. The C(4)-C(6) bond length is 1.99 Å. In the fifth C site, C(5) is bonded in a distorted single-bond geometry to one C(3) and one C(4) atom. In the sixth C site, C(6) is bonded in a 2-coordinate geometry to one Nb(2), one C(3), and one C(4) atom.