data_MgNb3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.86
_cell_length_b   5.86
_cell_length_c   5.86
_cell_angle_alpha   153.42
_cell_angle_beta   63.77
_cell_angle_gamma   123.21
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgNb3
_chemical_formula_sum   'Mg1 Nb3'
_cell_volume   74.54
_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  0.12  1.0
  Nb  Nb1  1  0.0  0.97  0.15  1.0
  Nb  Nb2  1  0.35  0.51  0.93  1.0
  Nb  Nb3  1  0.0  0.46  0.72  1.0

data_MgNb3
_symmetry_space_group_name_H-M   P1
_cell_length_a   2.69
_cell_length_b   5.57
_cell_length_c   5.86
_cell_angle_alpha   118.4
_cell_angle_beta   103.29
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgNb3
_chemical_formula_sum   'Mg1 Nb3'
_cell_volume   74.54
_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  0.88  0.88  1.0
  Nb  Nb1  1  0.17  0.58  0.23  1.0
  Nb  Nb2  1  0.46  0.74  0.74  1.0
  Nb  Nb3  1  0.97  0.82  0.82  1.0

Mg Nb Nb Nb
MgNb3 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a single-bond geometry to one Nb(1), two equivalent Nb(2), and two equivalent Nb(3) atoms. The Mg(1)-Nb(1) bond length is 0.33 Å. There is one shorter (3.19 Å) and one longer (3.40 Å) Mg(1)-Nb(2) bond length. There is one shorter (1.49 Å) and one longer (1.62 Å) Mg(1)-Nb(3) bond length. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a single-bond geometry to one Mg(1) and two equivalent Nb(3) atoms. There is one shorter (1.35 Å) and one longer (1.49 Å) Nb(1)-Nb(3) bond length. In the second Nb site, Nb(2) is bonded to two equivalent Mg(1), one Nb(3), and two equivalent Nb(2) atoms to form distorted corner-sharing NbMg2Nb3 trigonal bipyramids. The Nb(2)-Nb(3) bond length is 2.58 Å. Both Nb(2)-Nb(2) bond lengths are 2.69 Å. In the third Nb site, Nb(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Nb(2), and two equivalent Nb(1) atoms.