The material described by FeAsO4 crystallizes in the orthorhombic Imma space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, and corners with four equivalent As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are two inequivalent As sites. In the first As site, As(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-55°. In the second As site, As(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-57°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(2) and one As(2) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one As(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Fe(2) and one As(1) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_FeAsO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.273
_cell_length_b   9.273
_cell_length_c   9.273
_cell_angle_alpha   138.659
_cell_angle_beta   108.448
_cell_angle_gamma   86.143
_symmetry_Int_Tables_number   1
_cell_volume   480.836
_cell_formula_units_Z   6
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  0.000  0.500  0.500  1.0
  Fe  Fe1  1  0.500  0.000  0.500  1.0
  Fe  Fe2  1  0.887  0.887  0.500  1.0
  Fe  Fe3  1  0.613  0.113  1.000  1.0
  Fe  Fe4  1  0.113  0.113  0.500  1.0
  Fe  Fe5  1  0.387  0.887  0.000  1.0
  As  As6  1  0.250  0.817  0.567  1.0
  As  As7  1  0.750  0.183  0.433  1.0
  As  As8  1  0.823  0.323  0.000  1.0
  As  As9  1  0.677  0.677  0.500  1.0
  As  As10  1  0.177  0.677  1.000  1.0
  As  As11  1  0.323  0.323  0.500  1.0
  O  O12  1  0.123  0.974  0.597  1.0
  O  O13  1  0.377  0.974  0.851  1.0
  O  O14  1  0.623  0.026  0.149  1.0
  O  O15  1  0.877  0.026  0.403  1.0
  O  O16  1  0.144  0.579  0.435  1.0
  O  O17  1  0.356  0.791  0.435  1.0
  O  O18  1  0.856  0.421  0.565  1.0
  O  O19  1  0.644  0.209  0.565  1.0
  O  O20  1  0.140  0.403  0.824  1.0
  O  O21  1  0.360  0.183  0.263  1.0
  O  O22  1  0.421  0.597  0.737  1.0
  O  O23  1  0.079  0.817  0.176  1.0
  O  O24  1  0.651  0.805  0.425  1.0
  O  O25  1  0.849  0.274  0.154  1.0
  O  O26  1  0.620  0.195  0.846  1.0
  O  O27  1  0.880  0.726  0.575  1.0
  O  O28  1  0.349  0.195  0.575  1.0
  O  O29  1  0.151  0.726  0.846  1.0
  O  O30  1  0.380  0.805  0.154  1.0
  O  O31  1  0.120  0.274  0.425  1.0
  O  O32  1  0.921  0.183  0.824  1.0
  O  O33  1  0.579  0.403  0.263  1.0
  O  O34  1  0.640  0.817  0.737  1.0
  O  O35  1  0.860  0.597  0.176  1.0
[/CIF]
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The material described by FeAsO4 crystallizes in the orthorhombic Imma space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, and corners with four equivalent As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are two inequivalent As sites. In the first As site, As(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-55°. In the second As site, As(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-57°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(2) and one As(2) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one As(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Fe(2) and one As(1) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one As(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_FeAsO4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.273
_cell_length_b   9.273
_cell_length_c   9.273
_cell_angle_alpha   138.659
_cell_angle_beta   108.448
_cell_angle_gamma   86.143
_symmetry_Int_Tables_number   1
_cell_volume   480.836
_cell_formula_units_Z   6
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  0.000  0.500  0.500  1.0
  Fe  Fe1  1  0.500  0.000  0.500  1.0
  Fe  Fe2  1  0.887  0.887  0.500  1.0
  Fe  Fe3  1  0.613  0.113  1.000  1.0
  Fe  Fe4  1  0.113  0.113  0.500  1.0
  Fe  Fe5  1  0.387  0.887  0.000  1.0
  As  As6  1  0.250  0.817  0.567  1.0
  As  As7  1  0.750  0.183  0.433  1.0
  As  As8  1  0.823  0.323  0.000  1.0
  As  As9  1  0.677  0.677  0.500  1.0
  As  As10  1  0.177  0.677  1.000  1.0
  As  As11  1  0.323  0.323  0.500  1.0
  O  O12  1  0.123  0.974  0.597  1.0
  O  O13  1  0.377  0.974  0.851  1.0
  O  O14  1  0.623  0.026  0.149  1.0
  O  O15  1  0.877  0.026  0.403  1.0
  O  O16  1  0.144  0.579  0.435  1.0
  O  O17  1  0.356  0.791  0.435  1.0
  O  O18  1  0.856  0.421  0.565  1.0
  O  O19  1  0.644  0.209  0.565  1.0
  O  O20  1  0.140  0.403  0.824  1.0
  O  O21  1  0.360  0.183  0.263  1.0
  O  O22  1  0.421  0.597  0.737  1.0
  O  O23  1  0.079  0.817  0.176  1.0
  O  O24  1  0.651  0.805  0.425  1.0
  O  O25  1  0.849  0.274  0.154  1.0
  O  O26  1  0.620  0.195  0.846  1.0
  O  O27  1  0.880  0.726  0.575  1.0
  O  O28  1  0.349  0.195  0.575  1.0
  O  O29  1  0.151  0.726  0.846  1.0
  O  O30  1  0.380  0.805  0.154  1.0
  O  O31  1  0.120  0.274  0.425  1.0
  O  O32  1  0.921  0.183  0.824  1.0
  O  O33  1  0.579  0.403  0.263  1.0
  O  O34  1  0.640  0.817  0.737  1.0
  O  O35  1  0.860  0.597  0.176  1.0
[/CIF]
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