data_K2NbSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.61
_cell_length_b   3.61
_cell_length_c   10.62
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   K2NbSi
_chemical_formula_sum   'K2 Nb1 Si1'
_cell_volume   138.08
_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  0.8  0.8  0.92  1.0
  K  K1  1  0.0  0.0  0.41  1.0
  Nb  Nb2  1  0.8  0.8  0.53  1.0
  Si  Si3  1  0.0  0.0  0.69  1.0

data_K2NbSi
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.1
_cell_length_b   5.1
_cell_length_c   10.62
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   K2NbSi
_chemical_formula_sum   'K4 Nb2 Si2'
_cell_volume   276.16
_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  2  0.0  0.0  0.41  1.0
  K  K1  2  0.3  0.5  0.92  1.0
  Nb  Nb2  2  0.3  0.5  0.53  1.0
  Si  Si3  2  0.0  0.0  0.69  1.0

K K Nb Si
K K Nb Si 0 3 + + o 1 2 - - o 2 3 + + o 
K2NbSi crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two K2NbSi clusters. There are two inequivalent K sites. In the first K site, K(1) is bonded in a single-bond geometry to one Si(1) atom. The K(1)-Si(1) bond length is 2.62 Å. In the second K site, K(2) is bonded in a single-bond geometry to one Nb(1) atom. The K(2)-Nb(1) bond length is 1.61 Å. Nb(1) is bonded in a 2-coordinate geometry to one K(2) and one Si(1) atom. The Nb(1)-Si(1) bond length is 2.02 Å. Si(1) is bonded in a bent 120 degrees geometry to one K(1) and one Nb(1) atom.