data_KSi2As
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.56
_cell_length_b   3.56
_cell_length_c   7.0
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   KSi2As
_chemical_formula_sum   'K1 Si2 As1'
_cell_volume   88.57
_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  K1  1  0.0  0.0  0.28  1.0
  Si  Si2  1  0.78  0.78  0.61  1.0
  Si  Si3  1  0.0  0.0  0.68  1.0
  As  As0  1  0.78  0.78  0.94  1.0

data_KSi2As
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.03
_cell_length_b   5.03
_cell_length_c   7.0
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   KSi2As
_chemical_formula_sum   'K2 Si4 As2'
_cell_volume   177.13
_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  0.28  1.0
  Si  Si1  2  0.0  0.0  0.68  1.0
  Si  Si2  2  0.28  0.5  0.61  1.0
  As  As3  2  0.28  0.5  0.94  1.0

K Si Si As
K Si Si As 0 3 - - - 0 1 - - o 0 2 o o o 1 2 + + o 1 3 o o o 2 3 - - o 
KSi2As crystallizes in the monoclinic Cm space group. K(1) is bonded in a 2-coordinate geometry to one Si(1) and three equivalent As(1) atoms. The K(1)-Si(1) bond length is 2.56 Å. There is one shorter (2.59 Å) and two longer (3.71 Å) K(1)-As(1) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 3-coordinate geometry to one K(1), one Si(2), and one As(1) atom. The Si(1)-Si(2) bond length is 1.22 Å. The Si(1)-As(1) bond length is 2.34 Å. In the second Si site, Si(2) is bonded in a 2-coordinate geometry to one Si(1) and one As(1) atom. The Si(2)-As(1) bond length is 2.15 Å. As(1) is bonded in a 5-coordinate geometry to three equivalent K(1), one Si(1), and one Si(2) atom.