data_Mg2NbSe
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.97
_cell_length_b   4.81
_cell_length_c   5.69
_cell_angle_alpha   90.0
_cell_angle_beta   102.68
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2NbSe
_chemical_formula_sum   'Mg2 Nb1 Se1'
_cell_volume   79.37
_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  0.82  0.41  0.53  1.0
  Mg  Mg1  1  0.77  0.0  0.5  1.0
  Nb  Nb2  1  0.35  0.41  0.86  1.0
  Se  Se3  1  0.39  0.0  0.0  1.0

data_Mg2NbSe
_symmetry_space_group_name_H-M   P1
_cell_length_a   2.97
_cell_length_b   4.81
_cell_length_c   5.69
_cell_angle_alpha   90.0
_cell_angle_beta   102.68
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2NbSe
_chemical_formula_sum   'Mg2 Nb1 Se1'
_cell_volume   79.37
_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  0.77  0.0  0.5  1.0
  Mg  Mg1  1  0.82  0.41  0.53  1.0
  Nb  Nb2  1  0.35  0.41  0.86  1.0
  Se  Se3  1  0.39  0.0  0.0  1.0

Mg Mg Nb Se
Mg Mg Nb Se 0 1 o o o 0 2 + o o 2 3 o o + 
Mg2NbSe crystallizes in the triclinic P1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to one Mg(2) and two equivalent Nb(1) atoms. The Mg(1)-Mg(2) bond length is 1.97 Å. There is one shorter (2.18 Å) and one longer (2.59 Å) Mg(1)-Nb(1) bond length. In the second Mg site, Mg(2) is bonded in a 3-coordinate geometry to one Mg(1) and two equivalent Se(1) atoms. There is one shorter (2.80 Å) and one longer (3.05 Å) Mg(2)-Se(1) bond length. Nb(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Se(1) atoms. There is one shorter (2.11 Å) and one longer (2.96 Å) Nb(1)-Se(1) bond length. Se(1) is bonded in a 1-coordinate geometry to two equivalent Mg(2) and two equivalent Nb(1) atoms.