The material described by Cr2P2O9 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(3), one O(4), one O(6), one O(7), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent Cr(2)O6 octahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and edges with two equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(6), and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(2)O6 octahedra and corners with three equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-53°. In the second P site, P(2) is bonded to one O(4), one O(7), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(2)O6 octahedra and  an edgeedge with one Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(4) is bonded in an L-shaped geometry to one Cr(1) and one P(2) atom. In the second O site, O(5) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the third O site, O(6) is bonded in a linear geometry to one Cr(1) and one P(1) atom. In the fourth O site, O(7) is bonded in an L-shaped geometry to one Cr(1) and one P(2) atom. In the fifth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cr(2) and one P(2) atom. In the sixth O site, O(2) is bonded in a trigonal planar geometry to two equivalent Cr(2) and one P(1) atom. In the seventh O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Cr2P2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.355
_cell_length_b   7.756
_cell_length_c   13.778
_cell_angle_alpha   90.039
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   679.111
_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
  Cr  Cr0  1  0.750  0.349  0.882  1.0
  Cr  Cr1  1  0.250  0.651  0.118  1.0
  Cr  Cr2  1  0.250  0.849  0.618  1.0
  Cr  Cr3  1  0.750  0.151  0.382  1.0
  Cr  Cr4  1  0.500  0.000  0.000  1.0
  Cr  Cr5  1  0.500  0.500  0.500  1.0
  Cr  Cr6  1  1.000  0.500  0.500  1.0
  Cr  Cr7  1  1.000  0.000  0.000  1.0
  P  P8  1  0.250  0.348  0.938  1.0
  P  P9  1  0.750  0.652  0.062  1.0
  P  P10  1  0.750  0.848  0.562  1.0
  P  P11  1  0.250  0.152  0.438  1.0
  P  P12  1  0.750  0.393  0.692  1.0
  P  P13  1  0.750  0.107  0.192  1.0
  P  P14  1  0.250  0.893  0.808  1.0
  P  P15  1  0.250  0.607  0.308  1.0
  O  O16  1  0.050  0.595  0.371  1.0
  O  O17  1  0.550  0.405  0.629  1.0
  O  O18  1  0.950  0.095  0.129  1.0
  O  O19  1  0.450  0.905  0.871  1.0
  O  O20  1  0.950  0.405  0.629  1.0
  O  O21  1  0.450  0.595  0.371  1.0
  O  O22  1  0.050  0.905  0.871  1.0
  O  O23  1  0.550  0.095  0.129  1.0
  O  O24  1  0.250  0.338  0.486  1.0
  O  O25  1  0.750  0.662  0.514  1.0
  O  O26  1  0.750  0.838  0.014  1.0
  O  O27  1  0.250  0.162  0.986  1.0
  O  O28  1  0.750  0.145  0.952  1.0
  O  O29  1  0.250  0.855  0.048  1.0
  O  O30  1  0.250  0.645  0.548  1.0
  O  O31  1  0.750  0.355  0.452  1.0
  O  O32  1  0.750  0.226  0.756  1.0
  O  O33  1  0.250  0.774  0.244  1.0
  O  O34  1  0.250  0.726  0.744  1.0
  O  O35  1  0.750  0.274  0.256  1.0
  O  O36  1  0.446  0.139  0.375  1.0
  O  O37  1  0.946  0.861  0.625  1.0
  O  O38  1  0.554  0.639  0.125  1.0
  O  O39  1  0.054  0.361  0.875  1.0
  O  O40  1  0.554  0.861  0.625  1.0
  O  O41  1  0.054  0.139  0.375  1.0
  O  O42  1  0.446  0.361  0.875  1.0
  O  O43  1  0.946  0.639  0.125  1.0
  O  O44  1  0.750  0.515  0.981  1.0
  O  O45  1  0.250  0.030  0.725  1.0
  O  O46  1  0.250  0.470  0.225  1.0
  O  O47  1  0.750  0.530  0.775  1.0
  O  O48  1  0.750  0.985  0.481  1.0
  O  O49  1  0.250  0.016  0.519  1.0
  O  O50  1  0.250  0.485  0.019  1.0
  O  O51  1  0.750  0.970  0.275  1.0
[/CIF]
.
The material described by Cr2P2O9 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(3), one O(4), one O(6), one O(7), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent Cr(2)O6 octahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and edges with two equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(6), and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(2)O6 octahedra and corners with three equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-53°. In the second P site, P(2) is bonded to one O(4), one O(7), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(2)O6 octahedra and  an edgeedge with one Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(4) is bonded in an L-shaped geometry to one Cr(1) and one P(2) atom. In the second O site, O(5) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the third O site, O(6) is bonded in a linear geometry to one Cr(1) and one P(1) atom. In the fourth O site, O(7) is bonded in an L-shaped geometry to one Cr(1) and one P(2) atom. In the fifth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cr(2) and one P(2) atom. In the sixth O site, O(2) is bonded in a trigonal planar geometry to two equivalent Cr(2) and one P(1) atom. In the seventh O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Cr(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Cr2P2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.355
_cell_length_b   7.756
_cell_length_c   13.778
_cell_angle_alpha   90.039
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   679.111
_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
  Cr  Cr0  1  0.750  0.349  0.882  1.0
  Cr  Cr1  1  0.250  0.651  0.118  1.0
  Cr  Cr2  1  0.250  0.849  0.618  1.0
  Cr  Cr3  1  0.750  0.151  0.382  1.0
  Cr  Cr4  1  0.500  0.000  0.000  1.0
  Cr  Cr5  1  0.500  0.500  0.500  1.0
  Cr  Cr6  1  1.000  0.500  0.500  1.0
  Cr  Cr7  1  1.000  0.000  0.000  1.0
  P  P8  1  0.250  0.348  0.938  1.0
  P  P9  1  0.750  0.652  0.062  1.0
  P  P10  1  0.750  0.848  0.562  1.0
  P  P11  1  0.250  0.152  0.438  1.0
  P  P12  1  0.750  0.393  0.692  1.0
  P  P13  1  0.750  0.107  0.192  1.0
  P  P14  1  0.250  0.893  0.808  1.0
  P  P15  1  0.250  0.607  0.308  1.0
  O  O16  1  0.050  0.595  0.371  1.0
  O  O17  1  0.550  0.405  0.629  1.0
  O  O18  1  0.950  0.095  0.129  1.0
  O  O19  1  0.450  0.905  0.871  1.0
  O  O20  1  0.950  0.405  0.629  1.0
  O  O21  1  0.450  0.595  0.371  1.0
  O  O22  1  0.050  0.905  0.871  1.0
  O  O23  1  0.550  0.095  0.129  1.0
  O  O24  1  0.250  0.338  0.486  1.0
  O  O25  1  0.750  0.662  0.514  1.0
  O  O26  1  0.750  0.838  0.014  1.0
  O  O27  1  0.250  0.162  0.986  1.0
  O  O28  1  0.750  0.145  0.952  1.0
  O  O29  1  0.250  0.855  0.048  1.0
  O  O30  1  0.250  0.645  0.548  1.0
  O  O31  1  0.750  0.355  0.452  1.0
  O  O32  1  0.750  0.226  0.756  1.0
  O  O33  1  0.250  0.774  0.244  1.0
  O  O34  1  0.250  0.726  0.744  1.0
  O  O35  1  0.750  0.274  0.256  1.0
  O  O36  1  0.446  0.139  0.375  1.0
  O  O37  1  0.946  0.861  0.625  1.0
  O  O38  1  0.554  0.639  0.125  1.0
  O  O39  1  0.054  0.361  0.875  1.0
  O  O40  1  0.554  0.861  0.625  1.0
  O  O41  1  0.054  0.139  0.375  1.0
  O  O42  1  0.446  0.361  0.875  1.0
  O  O43  1  0.946  0.639  0.125  1.0
  O  O44  1  0.750  0.515  0.981  1.0
  O  O45  1  0.250  0.030  0.725  1.0
  O  O46  1  0.250  0.470  0.225  1.0
  O  O47  1  0.750  0.530  0.775  1.0
  O  O48  1  0.750  0.985  0.481  1.0
  O  O49  1  0.250  0.016  0.519  1.0
  O  O50  1  0.250  0.485  0.019  1.0
  O  O51  1  0.750  0.970  0.275  1.0
[/CIF]
.