The material structure described by FeAsO4 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(1), one O(2), one O(3), and two equivalent O(4) atoms to form distorted FeO5 trigonal bipyramids that share corners with five equivalent As(1)O4 tetrahedra and  an edgeedge with one Fe(1)O5 trigonal bipyramid. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with five equivalent Fe(1)O5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one As(1) atom. is represented by the CIF file [CIF]
data_FeAsO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.144
_cell_length_b   5.046
_cell_length_c   7.967
_cell_angle_alpha   66.723
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   300.757
_cell_formula_units_Z   4
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
  Fe  Fe0  1  0.960  0.409  0.327  1.0
  Fe  Fe1  1  0.460  0.591  0.173  1.0
  Fe  Fe2  1  0.040  0.591  0.673  1.0
  Fe  Fe3  1  0.540  0.409  0.827  1.0
  As  As4  1  0.202  0.151  0.074  1.0
  As  As5  1  0.702  0.849  0.426  1.0
  As  As6  1  0.798  0.849  0.926  1.0
  As  As7  1  0.298  0.151  0.574  1.0
  O  O8  1  0.264  0.808  0.132  1.0
  O  O9  1  0.764  0.192  0.368  1.0
  O  O10  1  0.736  0.192  0.868  1.0
  O  O11  1  0.236  0.808  0.632  1.0
  O  O12  1  0.076  0.264  0.890  1.0
  O  O13  1  0.576  0.736  0.610  1.0
  O  O14  1  0.924  0.736  0.110  1.0
  O  O15  1  0.424  0.264  0.390  1.0
  O  O16  1  0.398  0.173  0.753  1.0
  O  O17  1  0.898  0.827  0.747  1.0
  O  O18  1  0.602  0.827  0.247  1.0
  O  O19  1  0.102  0.173  0.253  1.0
  O  O20  1  0.127  0.369  0.522  1.0
  O  O21  1  0.627  0.631  0.978  1.0
  O  O22  1  0.873  0.631  0.478  1.0
  O  O23  1  0.373  0.369  0.022  1.0
[/CIF]
.
The material structure described by FeAsO4 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(1), one O(2), one O(3), and two equivalent O(4) atoms to form distorted FeO5 trigonal bipyramids that share corners with five equivalent As(1)O4 tetrahedra and  an edgeedge with one Fe(1)O5 trigonal bipyramid. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with five equivalent Fe(1)O5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one As(1) atom. is represented by the CIF file [CIF]
data_FeAsO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.144
_cell_length_b   5.046
_cell_length_c   7.967
_cell_angle_alpha   66.723
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   300.757
_cell_formula_units_Z   4
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
  Fe  Fe0  1  0.960  0.409  0.327  1.0
  Fe  Fe1  1  0.460  0.591  0.173  1.0
  Fe  Fe2  1  0.040  0.591  0.673  1.0
  Fe  Fe3  1  0.540  0.409  0.827  1.0
  As  As4  1  0.202  0.151  0.074  1.0
  As  As5  1  0.702  0.849  0.426  1.0
  As  As6  1  0.798  0.849  0.926  1.0
  As  As7  1  0.298  0.151  0.574  1.0
  O  O8  1  0.264  0.808  0.132  1.0
  O  O9  1  0.764  0.192  0.368  1.0
  O  O10  1  0.736  0.192  0.868  1.0
  O  O11  1  0.236  0.808  0.632  1.0
  O  O12  1  0.076  0.264  0.890  1.0
  O  O13  1  0.576  0.736  0.610  1.0
  O  O14  1  0.924  0.736  0.110  1.0
  O  O15  1  0.424  0.264  0.390  1.0
  O  O16  1  0.398  0.173  0.753  1.0
  O  O17  1  0.898  0.827  0.747  1.0
  O  O18  1  0.602  0.827  0.247  1.0
  O  O19  1  0.102  0.173  0.253  1.0
  O  O20  1  0.127  0.369  0.522  1.0
  O  O21  1  0.627  0.631  0.978  1.0
  O  O22  1  0.873  0.631  0.478  1.0
  O  O23  1  0.373  0.369  0.022  1.0
[/CIF]
.