The structure described by SrFe3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Sr(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Fe(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, 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 48-60°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Fe(2)O6 octahedra, 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 39-60°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Fe(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Fe(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Sr(1), one Fe(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), one Fe(1), one Fe(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Fe(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. is represented by the CIF file [CIF]
data_SrFe3(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.658
_cell_length_b   7.875
_cell_length_c   9.710
_cell_angle_alpha   90.000
_cell_angle_beta   112.253
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   541.910
_cell_formula_units_Z   2
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
  Sr  Sr0  1  0.500  0.500  0.500  1.0
  Sr  Sr1  1  0.500  0.000  0.000  1.0
  Fe  Fe2  1  0.189  0.624  0.027  1.0
  Fe  Fe3  1  0.000  0.000  0.000  1.0
  Fe  Fe4  1  0.189  0.876  0.527  1.0
  Fe  Fe5  1  0.811  0.376  0.973  1.0
  Fe  Fe6  1  0.811  0.124  0.473  1.0
  Fe  Fe7  1  0.000  0.500  0.500  1.0
  P  P8  1  0.604  0.055  0.704  1.0
  P  P9  1  0.396  0.555  0.796  1.0
  P  P10  1  0.396  0.945  0.296  1.0
  P  P11  1  0.604  0.445  0.204  1.0
  P  P12  1  0.887  0.797  0.692  1.0
  P  P13  1  0.113  0.297  0.808  1.0
  P  P14  1  0.887  0.703  0.192  1.0
  P  P15  1  0.113  0.203  0.308  1.0
  O  O16  1  0.841  0.627  0.610  1.0
  O  O17  1  0.159  0.127  0.890  1.0
  O  O18  1  0.159  0.373  0.390  1.0
  O  O19  1  0.841  0.873  0.110  1.0
  O  O20  1  0.275  0.610  0.634  1.0
  O  O21  1  0.725  0.110  0.866  1.0
  O  O22  1  0.725  0.390  0.366  1.0
  O  O23  1  0.275  0.890  0.134  1.0
  O  O24  1  0.620  0.180  0.590  1.0
  O  O25  1  0.380  0.680  0.910  1.0
  O  O26  1  0.380  0.820  0.410  1.0
  O  O27  1  0.620  0.320  0.090  1.0
  O  O28  1  0.685  0.872  0.678  1.0
  O  O29  1  0.315  0.372  0.822  1.0
  O  O30  1  0.315  0.128  0.322  1.0
  O  O31  1  0.685  0.628  0.178  1.0
  O  O32  1  0.405  0.490  0.194  1.0
  O  O33  1  0.595  0.990  0.306  1.0
  O  O34  1  0.595  0.510  0.806  1.0
  O  O35  1  0.405  0.010  0.694  1.0
  O  O36  1  0.001  0.214  0.139  1.0
  O  O37  1  0.999  0.714  0.361  1.0
  O  O38  1  0.972  0.921  0.613  1.0
  O  O39  1  0.001  0.286  0.639  1.0
  O  O40  1  0.972  0.579  0.113  1.0
  O  O41  1  0.028  0.079  0.387  1.0
  O  O42  1  0.028  0.421  0.887  1.0
  O  O43  1  0.999  0.786  0.861  1.0
[/CIF]
.
The structure described by SrFe3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Sr(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form FeO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Fe(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, 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 48-60°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Fe(2)O6 octahedra, 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 39-60°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Fe(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Fe(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Sr(1), one Fe(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), one Fe(1), one Fe(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Fe(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. is represented by the CIF file [CIF]
data_SrFe3(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.658
_cell_length_b   7.875
_cell_length_c   9.710
_cell_angle_alpha   90.000
_cell_angle_beta   112.253
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   541.910
_cell_formula_units_Z   2
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
  Sr  Sr0  1  0.500  0.500  0.500  1.0
  Sr  Sr1  1  0.500  0.000  0.000  1.0
  Fe  Fe2  1  0.189  0.624  0.027  1.0
  Fe  Fe3  1  0.000  0.000  0.000  1.0
  Fe  Fe4  1  0.189  0.876  0.527  1.0
  Fe  Fe5  1  0.811  0.376  0.973  1.0
  Fe  Fe6  1  0.811  0.124  0.473  1.0
  Fe  Fe7  1  0.000  0.500  0.500  1.0
  P  P8  1  0.604  0.055  0.704  1.0
  P  P9  1  0.396  0.555  0.796  1.0
  P  P10  1  0.396  0.945  0.296  1.0
  P  P11  1  0.604  0.445  0.204  1.0
  P  P12  1  0.887  0.797  0.692  1.0
  P  P13  1  0.113  0.297  0.808  1.0
  P  P14  1  0.887  0.703  0.192  1.0
  P  P15  1  0.113  0.203  0.308  1.0
  O  O16  1  0.841  0.627  0.610  1.0
  O  O17  1  0.159  0.127  0.890  1.0
  O  O18  1  0.159  0.373  0.390  1.0
  O  O19  1  0.841  0.873  0.110  1.0
  O  O20  1  0.275  0.610  0.634  1.0
  O  O21  1  0.725  0.110  0.866  1.0
  O  O22  1  0.725  0.390  0.366  1.0
  O  O23  1  0.275  0.890  0.134  1.0
  O  O24  1  0.620  0.180  0.590  1.0
  O  O25  1  0.380  0.680  0.910  1.0
  O  O26  1  0.380  0.820  0.410  1.0
  O  O27  1  0.620  0.320  0.090  1.0
  O  O28  1  0.685  0.872  0.678  1.0
  O  O29  1  0.315  0.372  0.822  1.0
  O  O30  1  0.315  0.128  0.322  1.0
  O  O31  1  0.685  0.628  0.178  1.0
  O  O32  1  0.405  0.490  0.194  1.0
  O  O33  1  0.595  0.990  0.306  1.0
  O  O34  1  0.595  0.510  0.806  1.0
  O  O35  1  0.405  0.010  0.694  1.0
  O  O36  1  0.001  0.214  0.139  1.0
  O  O37  1  0.999  0.714  0.361  1.0
  O  O38  1  0.972  0.921  0.613  1.0
  O  O39  1  0.001  0.286  0.639  1.0
  O  O40  1  0.972  0.579  0.113  1.0
  O  O41  1  0.028  0.079  0.387  1.0
  O  O42  1  0.028  0.421  0.887  1.0
  O  O43  1  0.999  0.786  0.861  1.0
[/CIF]
.