data_K3MgNb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.61
_cell_length_b   6.61
_cell_length_c   6.61
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   K3MgNb
_chemical_formula_sum   'K3 Mg1 Nb1'
_cell_volume   288.97
_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  K2  1  0.0  0.31  0.0  1.0
  K  K3  1  0.0  0.0  0.31  1.0
  K  K4  1  0.31  0.0  0.0  1.0
  Mg  Mg0  1  0.0  0.0  0.0  1.0
  Nb  Nb1  1  0.31  0.31  0.31  1.0

data_K3MgNb
_symmetry_space_group_name_H-M   R3m
_cell_length_a   9.35
_cell_length_b   9.35
_cell_length_c   11.45
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   K3MgNb
_chemical_formula_sum   'K9 Mg3 Nb3'
_cell_volume   866.91
_cell_formula_units_Z   3
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+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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
  K  K0  9  0.2  0.1  0.1  1.0
  Mg  Mg1  3  0.0  0.0  0.0  1.0
  Nb  Nb2  3  0.0  0.0  0.31  1.0

K K K Mg Nb
K3MgNb is Pb (Zr_0.50 Ti_0.48) O_3 structured and crystallizes in the trigonal R3m space group. The structure is zero-dimensional and consists of three K3MgNb clusters. K(1) is bonded in a distorted L-shaped geometry to one Mg(1) and one Nb(1) atom. The K(1)-Mg(1) bond length is 2.02 Å. The K(1)-Nb(1) bond length is 2.86 Å. Mg(1) is bonded in a distorted T-shaped geometry to three equivalent K(1) atoms. Nb(1) is bonded in a 3-coordinate geometry to three equivalent K(1) atoms.