data_Al2SiP
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.32
_cell_length_b   3.32
_cell_length_c   5.56
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Al2SiP
_chemical_formula_sum   'Al2 Si1 P1'
_cell_volume   61.43
_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
  Al  Al0  1  0.66  0.66  0.43  1.0
  Al  Al1  1  0.66  0.66  0.13  1.0
  Si  Si3  1  0.0  0.0  0.0  1.0
  P  P2  1  0.0  0.0  0.78  1.0

data_Al2SiP
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.7
_cell_length_b   4.7
_cell_length_c   5.56
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Al2SiP
_chemical_formula_sum   'Al4 Si2 P2'
_cell_volume   122.85
_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
  Al  Al0  2  0.16  0.5  0.13  1.0
  Al  Al1  2  0.16  0.5  0.43  1.0
  Si  Si2  2  0.0  0.0  0.0  1.0
  P  P3  2  0.0  0.0  0.78  1.0

Al Al Si P
Al Al Si P 0 1 o o o 1 2 + + o 2 3 o o - 
Al2SiP crystallizes in the monoclinic Cm space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a bent 150 degrees geometry to one Al(2) and one P(1) atom. The Al(1)-Al(2) bond length is 1.63 Å. The Al(1)-P(1) bond length is 2.53 Å. In the second Al site, Al(2) is bonded in a 4-coordinate geometry to one Al(1) and three equivalent Si(1) atoms. There is one shorter (1.76 Å) and two longer (2.58 Å) Al(2)-Si(1) bond lengths. Si(1) is bonded in a 2-coordinate geometry to three equivalent Al(2) and one P(1) atom. The Si(1)-P(1) bond length is 1.22 Å. P(1) is bonded in a distorted single-bond geometry to one Al(1) and one Si(1) atom.