data_Mg3C
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.99
_cell_length_b   2.99
_cell_length_c   7.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   105.29
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg3C
_chemical_formula_sum   'Mg3 C1'
_cell_volume   68.37
_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
  Mg  Mg1  1  0.81  0.0  0.61  1.0
  Mg  Mg2  1  0.0  0.0  0.97  1.0
  Mg  Mg3  1  0.81  0.0  0.33  1.0
  C  C0  1  0.0  0.0  0.0  1.0

data_Mg3C
_symmetry_space_group_name_H-M   P1
_cell_length_a   2.99
_cell_length_b   2.99
_cell_length_c   7.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   105.29
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg3C
_chemical_formula_sum   'Mg3 C1'
_cell_volume   68.37
_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
  Mg  Mg0  1  0.0  0.0  0.97  1.0
  Mg  Mg1  1  0.81  0.0  0.33  1.0
  Mg  Mg2  1  0.81  0.0  0.61  1.0
  C  C3  1  0.0  0.0  0.0  1.0

Mg Mg Mg C
Mg Mg Mg C 0 0 o + o 0 0 + o o 0 2 o o o 0 1 + o o 1 3 o o + 1 2 - o + 2 2 o + o 2 2 + o o 2 3 + o o 
Mg3C crystallizes in the triclinic P1 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Mg(2), one Mg(3), and four equivalent Mg(1) atoms to form a mixture of distorted edge and corner-sharing MgMg6 octahedra. The corner-sharing octahedra are not tilted. The Mg(1)-Mg(2) bond length is 2.90 Å. The Mg(1)-Mg(3) bond length is 2.25 Å. All Mg(1)-Mg(1) bond lengths are 2.99 Å. In the second Mg site, Mg(2) is bonded in a single-bond geometry to one Mg(1) and one C(1) atom. The Mg(2)-C(1) bond length is 0.24 Å. In the third Mg site, Mg(3) is bonded in a 1-coordinate geometry to one Mg(1) and one C(1) atom. The Mg(3)-C(1) bond length is 2.66 Å. C(1) is bonded in a single-bond geometry to one Mg(2) and one Mg(3) atom.