data_Si2AsP
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.51
_cell_length_b   3.51
_cell_length_c   5.66
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si2AsP
_chemical_formula_sum   'Si2 As1 P1'
_cell_volume   69.91
_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
  Si  Si2  1  0.76  0.76  0.8  1.0
  Si  Si3  1  0.0  0.0  0.82  1.0
  As  As0  1  0.76  0.76  0.36  1.0
  P  P1  1  0.0  0.0  0.17  1.0

data_Si2AsP
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.97
_cell_length_b   4.97
_cell_length_c   5.66
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Si2AsP
_chemical_formula_sum   'Si4 As2 P2'
_cell_volume   139.82
_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
  Si  Si0  2  0.0  0.0  0.82  1.0
  Si  Si1  2  0.26  0.5  0.8  1.0
  As  As2  2  0.26  0.5  0.36  1.0
  P  P3  2  0.0  0.0  0.17  1.0

Si Si As P
Si Si As P 0 1 + + o 2 3 + + o 
Si2AsP crystallizes in the monoclinic Cm space group. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 5-coordinate geometry to three equivalent Si(2), one As(1), and one P(1) atom. There is one shorter (1.21 Å) and two longer (2.80 Å) Si(1)-Si(2) bond lengths. The Si(1)-As(1) bond length is 2.51 Å. The Si(1)-P(1) bond length is 2.40 Å. In the second Si site, Si(2) is bonded in an L-shaped geometry to three equivalent Si(1) and one P(1) atom. The Si(2)-P(1) bond length is 2.01 Å. As(1) is bonded in a 2-coordinate geometry to one Si(1) and one P(1) atom. The As(1)-P(1) bond length is 1.62 Å. P(1) is bonded in a 2-coordinate geometry to one Si(1), one Si(2), and one As(1) atom.