The structure described by FeP2O7 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-51°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 40-45°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. is represented by the CIF file [CIF]
data_FeP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.251
_cell_length_b   6.985
_cell_length_c   9.538
_cell_angle_alpha   71.327
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   520.700
_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  0.269  0.277  0.507  1.0
  Fe  Fe1  1  0.231  0.277  0.007  1.0
  Fe  Fe2  1  0.769  0.723  0.993  1.0
  Fe  Fe3  1  0.731  0.723  0.493  1.0
  P  P4  1  0.917  0.464  0.794  1.0
  P  P5  1  0.083  0.536  0.206  1.0
  P  P6  1  0.533  0.932  0.705  1.0
  P  P7  1  0.467  0.068  0.295  1.0
  P  P8  1  0.967  0.932  0.205  1.0
  P  P9  1  0.583  0.464  0.294  1.0
  P  P10  1  0.417  0.536  0.706  1.0
  P  P11  1  0.033  0.068  0.795  1.0
  O  O12  1  0.085  0.475  0.860  1.0
  O  O13  1  0.585  0.525  0.640  1.0
  O  O14  1  0.099  0.108  0.639  1.0
  O  O15  1  0.395  0.765  0.707  1.0
  O  O16  1  0.170  0.080  0.901  1.0
  O  O17  1  0.219  0.494  0.109  1.0
  O  O18  1  0.908  0.602  0.634  1.0
  O  O19  1  0.105  0.765  0.207  1.0
  O  O20  1  0.670  0.920  0.599  1.0
  O  O21  1  0.944  0.867  0.848  1.0
  O  O22  1  0.915  0.525  0.140  1.0
  O  O23  1  0.444  0.133  0.652  1.0
  O  O24  1  0.719  0.506  0.391  1.0
  O  O25  1  0.401  0.108  0.139  1.0
  O  O26  1  0.415  0.475  0.360  1.0
  O  O27  1  0.056  0.133  0.152  1.0
  O  O28  1  0.605  0.235  0.293  1.0
  O  O29  1  0.556  0.867  0.348  1.0
  O  O30  1  0.408  0.398  0.866  1.0
  O  O31  1  0.830  0.920  0.099  1.0
  O  O32  1  0.781  0.506  0.891  1.0
  O  O33  1  0.599  0.892  0.861  1.0
  O  O34  1  0.281  0.494  0.609  1.0
  O  O35  1  0.330  0.080  0.401  1.0
  O  O36  1  0.092  0.398  0.366  1.0
  O  O37  1  0.895  0.235  0.793  1.0
  O  O38  1  0.592  0.602  0.134  1.0
  O  O39  1  0.901  0.892  0.361  1.0
[/CIF]
.
The structure described by FeP2O7 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-51°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 40-45°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. is represented by the CIF file [CIF]
data_FeP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.251
_cell_length_b   6.985
_cell_length_c   9.538
_cell_angle_alpha   71.327
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   520.700
_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  0.269  0.277  0.507  1.0
  Fe  Fe1  1  0.231  0.277  0.007  1.0
  Fe  Fe2  1  0.769  0.723  0.993  1.0
  Fe  Fe3  1  0.731  0.723  0.493  1.0
  P  P4  1  0.917  0.464  0.794  1.0
  P  P5  1  0.083  0.536  0.206  1.0
  P  P6  1  0.533  0.932  0.705  1.0
  P  P7  1  0.467  0.068  0.295  1.0
  P  P8  1  0.967  0.932  0.205  1.0
  P  P9  1  0.583  0.464  0.294  1.0
  P  P10  1  0.417  0.536  0.706  1.0
  P  P11  1  0.033  0.068  0.795  1.0
  O  O12  1  0.085  0.475  0.860  1.0
  O  O13  1  0.585  0.525  0.640  1.0
  O  O14  1  0.099  0.108  0.639  1.0
  O  O15  1  0.395  0.765  0.707  1.0
  O  O16  1  0.170  0.080  0.901  1.0
  O  O17  1  0.219  0.494  0.109  1.0
  O  O18  1  0.908  0.602  0.634  1.0
  O  O19  1  0.105  0.765  0.207  1.0
  O  O20  1  0.670  0.920  0.599  1.0
  O  O21  1  0.944  0.867  0.848  1.0
  O  O22  1  0.915  0.525  0.140  1.0
  O  O23  1  0.444  0.133  0.652  1.0
  O  O24  1  0.719  0.506  0.391  1.0
  O  O25  1  0.401  0.108  0.139  1.0
  O  O26  1  0.415  0.475  0.360  1.0
  O  O27  1  0.056  0.133  0.152  1.0
  O  O28  1  0.605  0.235  0.293  1.0
  O  O29  1  0.556  0.867  0.348  1.0
  O  O30  1  0.408  0.398  0.866  1.0
  O  O31  1  0.830  0.920  0.099  1.0
  O  O32  1  0.781  0.506  0.891  1.0
  O  O33  1  0.599  0.892  0.861  1.0
  O  O34  1  0.281  0.494  0.609  1.0
  O  O35  1  0.330  0.080  0.401  1.0
  O  O36  1  0.092  0.398  0.366  1.0
  O  O37  1  0.895  0.235  0.793  1.0
  O  O38  1  0.592  0.602  0.134  1.0
  O  O39  1  0.901  0.892  0.361  1.0
[/CIF]
.