data_K2MgNb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.03
_cell_length_b   6.03
_cell_length_c   4.28
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   K2MgNb
_chemical_formula_sum   'K2 Mg1 Nb1'
_cell_volume   155.67
_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
  K  K0  1  0.02  0.0  0.14  1.0
  K  K1  1  0.0  0.02  0.14  1.0
  Mg  Mg2  1  0.0  0.0  0.0  1.0
  Nb  Nb3  1  0.02  0.02  0.0  1.0

data_K2MgNb
_symmetry_space_group_name_H-M   Cm
_cell_length_a   8.53
_cell_length_b   8.53
_cell_length_c   4.28
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   K2MgNb
_chemical_formula_sum   'K4 Mg2 Nb2'
_cell_volume   311.35
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  K  K0  4  0.01  0.01  0.14  1.0
  Mg  Mg1  2  0.0  0.0  0.0  1.0
  Nb  Nb2  2  0.02  0.0  0.0  1.0

K K Mg Nb
(K)2MgNb crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two potassium molecules and two MgNb clusters. In each MgNb cluster, Mg(1) is bonded in a single-bond geometry to one Nb(1) atom. The Mg(1)-Nb(1) bond length is 0.14 Å. Nb(1) is bonded in a single-bond geometry to one Mg(1) atom.