data_Mg4C
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.17
_cell_length_b   8.17
_cell_length_c   8.17
_cell_angle_alpha   109.47
_cell_angle_beta   109.47
_cell_angle_gamma   109.47
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg4C
_chemical_formula_sum   'Mg16 C4'
_cell_volume   419.66
_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
  Mg  Mg4  1  0.53  0.53  0.53  1.0
  Mg  Mg5  1  0.81  0.19  0.19  1.0
  Mg  Mg6  1  0.19  0.81  0.19  1.0
  Mg  Mg7  1  0.19  0.19  0.81  1.0
  Mg  Mg8  1  0.0  0.0  0.09  1.0
  Mg  Mg9  1  0.0  0.0  0.35  1.0
  Mg  Mg10  1  0.0  0.09  0.0  1.0
  Mg  Mg11  1  0.0  0.35  0.0  1.0
  Mg  Mg12  1  0.09  0.0  0.0  1.0
  Mg  Mg13  1  0.35  0.0  0.0  1.0
  Mg  Mg14  1  0.72  0.0  0.36  1.0
  Mg  Mg15  1  0.0  0.72  0.36  1.0
  Mg  Mg16  1  0.0  0.36  0.72  1.0
  Mg  Mg17  1  0.72  0.36  0.0  1.0
  Mg  Mg18  1  0.36  0.72  0.0  1.0
  Mg  Mg19  1  0.36  0.0  0.72  1.0
  C  C0  1  0.34  0.34  0.34  1.0
  C  C1  1  0.62  0.38  0.38  1.0
  C  C2  1  0.38  0.62  0.38  1.0
  C  C3  1  0.38  0.38  0.62  1.0

data_Mg4C
_symmetry_space_group_name_H-M   R3m
_cell_length_a   13.34
_cell_length_b   13.34
_cell_length_c   8.17
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Mg4C
_chemical_formula_sum   'Mg48 C12'
_cell_volume   1258.99
_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  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+2/3, y+1/3, z+1/3'
  8  '-y+2/3, x-y+1/3, z+1/3'
  9  '-x+y+2/3, -x+1/3, z+1/3'
  10  '-y+2/3, -x+1/3, z+1/3'
  11  '-x+y+2/3, y+1/3, z+1/3'
  12  'x+2/3, x-y+1/3, z+1/3'
  13  'x+1/3, y+2/3, z+2/3'
  14  '-y+1/3, x-y+2/3, z+2/3'
  15  '-x+y+1/3, -x+2/3, z+2/3'
  16  '-y+1/3, -x+2/3, z+2/3'
  17  '-x+y+1/3, y+2/3, z+2/3'
  18  'x+1/3, x-y+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
  Mg  Mg0  18  0.0  0.36  0.36  1.0
  Mg  Mg1  9  0.06  0.03  0.03  1.0
  Mg  Mg2  9  0.08  0.54  0.73  1.0
  Mg  Mg3  9  0.22  0.44  0.78  1.0
  Mg  Mg4  3  0.0  0.0  0.53  1.0
  C  C5  9  0.17  0.08  0.46  1.0
  C  C6  3  0.0  0.0  0.34  1.0

Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg Mg C C C C
Mg4C crystallizes in the trigonal R3m space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted single-bond geometry to one C(1) and three equivalent C(2) atoms. The Mg(1)-C(1) bond length is 1.52 Å. All Mg(1)-C(2) bond lengths are 1.99 Å. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Mg(5) atoms. Both Mg(2)-Mg(5) bond lengths are 2.49 Å. In the third Mg site, Mg(3) is bonded in a 4-coordinate geometry to one Mg(4), two equivalent Mg(3), and one C(1) atom. The Mg(3)-Mg(4) bond length is 2.12 Å. Both Mg(3)-Mg(3) bond lengths are 1.16 Å. The Mg(3)-C(1) bond length is 2.63 Å. In the fourth Mg site, Mg(4) is bonded in a 4-coordinate geometry to one Mg(3), two equivalent Mg(5), and one C(2) atom. Both Mg(4)-Mg(5) bond lengths are 2.35 Å. The Mg(4)-C(2) bond length is 2.91 Å. In the fifth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Mg(2), one Mg(4), and two equivalent Mg(5) atoms. Both Mg(5)-Mg(5) bond lengths are 2.78 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a single-bond geometry to one Mg(1) and three equivalent Mg(3) atoms. In the second C site, C(2) is bonded in a single-bond geometry to one Mg(1) and one Mg(4) atom.