The compound described by FeAs2O7 crystallizes in the monoclinic C2 space group. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent As(1)O4 tetrahedra. 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 three equivalent Fe(1)O6 octahedra and  a cornercorner with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(1) atom. In the second O site, O(2) is bonded in a bent 120 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 bent 120 degrees geometry to two equivalent As(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_FeAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.340
_cell_length_b   5.340
_cell_length_c   4.836
_cell_angle_alpha   81.668
_cell_angle_beta   81.668
_cell_angle_gamma   100.692
_symmetry_Int_Tables_number   1
_cell_volume   131.950
_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
  Fe  Fe0  1  0.885  0.115  0.000  1.0
  As  As1  1  0.324  0.254  0.408  1.0
  As  As2  1  0.746  0.676  0.592  1.0
  O  O3  1  0.172  0.051  0.718  1.0
  O  O4  1  0.137  0.345  0.166  1.0
  O  O5  1  0.577  0.133  0.273  1.0
  O  O6  1  0.949  0.828  0.282  1.0
  O  O7  1  0.655  0.863  0.834  1.0
  O  O8  1  0.867  0.423  0.727  1.0
  O  O9  1  0.439  0.561  0.500  1.0
[/CIF]
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The compound described by FeAs2O7 crystallizes in the monoclinic C2 space group. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent As(1)O4 tetrahedra. 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 three equivalent Fe(1)O6 octahedra and  a cornercorner with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(1) atom. In the second O site, O(2) is bonded in a bent 120 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 bent 120 degrees geometry to two equivalent As(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_FeAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.340
_cell_length_b   5.340
_cell_length_c   4.836
_cell_angle_alpha   81.668
_cell_angle_beta   81.668
_cell_angle_gamma   100.692
_symmetry_Int_Tables_number   1
_cell_volume   131.950
_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
  Fe  Fe0  1  0.885  0.115  0.000  1.0
  As  As1  1  0.324  0.254  0.408  1.0
  As  As2  1  0.746  0.676  0.592  1.0
  O  O3  1  0.172  0.051  0.718  1.0
  O  O4  1  0.137  0.345  0.166  1.0
  O  O5  1  0.577  0.133  0.273  1.0
  O  O6  1  0.949  0.828  0.282  1.0
  O  O7  1  0.655  0.863  0.834  1.0
  O  O8  1  0.867  0.423  0.727  1.0
  O  O9  1  0.439  0.561  0.500  1.0
[/CIF]
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