The structure described by K2CuP2O7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(3), and four equivalent O(5) atoms. In the second K site, K(2) is bonded in a 9-coordinate geometry to one O(1), two equivalent O(2), two equivalent O(5), and four equivalent O(3) atoms. Cu(1) is bonded to one O(1), two equivalent O(3), and two equivalent O(5) atoms to form CuO5 square pyramids that share corners with two 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(2), one O(4), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(2)O4 tetrahedra. In the second P site, P(2) is bonded to one O(1), one O(4), and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with three equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(1)O4 tetrahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), one Cu(1), and one P(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one P(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one K(1), two equivalent K(2), one Cu(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one K(2), two equivalent K(1), one Cu(1), and one P(2) atom. is represented by the CIF card [CIF]
data_K2CuP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.260
_cell_length_b   9.486
_cell_length_c   14.174
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   707.201
_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
  K  K0  1  0.750  0.376  0.299  1.0
  K  K1  1  0.250  0.624  0.701  1.0
  K  K2  1  0.750  0.630  0.090  1.0
  K  K3  1  0.750  0.870  0.590  1.0
  K  K4  1  0.750  0.124  0.799  1.0
  K  K5  1  0.250  0.876  0.201  1.0
  K  K6  1  0.250  0.370  0.910  1.0
  K  K7  1  0.250  0.130  0.410  1.0
  Cu  Cu8  1  0.250  0.251  0.170  1.0
  Cu  Cu9  1  0.250  0.249  0.670  1.0
  Cu  Cu10  1  0.750  0.749  0.830  1.0
  Cu  Cu11  1  0.750  0.751  0.330  1.0
  P  P12  1  0.250  0.724  0.947  1.0
  P  P13  1  0.250  0.776  0.447  1.0
  P  P14  1  0.750  0.068  0.194  1.0
  P  P15  1  0.250  0.568  0.306  1.0
  P  P16  1  0.750  0.224  0.553  1.0
  P  P17  1  0.750  0.276  0.053  1.0
  P  P18  1  0.250  0.932  0.806  1.0
  P  P19  1  0.750  0.432  0.694  1.0
  O  O20  1  0.750  0.589  0.699  1.0
  O  O21  1  0.250  0.720  0.052  1.0
  O  O22  1  0.512  0.157  0.597  1.0
  O  O23  1  0.250  0.889  0.916  1.0
  O  O24  1  0.250  0.089  0.801  1.0
  O  O25  1  0.992  0.134  0.235  1.0
  O  O26  1  0.508  0.134  0.235  1.0
  O  O27  1  0.008  0.634  0.265  1.0
  O  O28  1  0.988  0.343  0.097  1.0
  O  O29  1  0.250  0.780  0.552  1.0
  O  O30  1  0.508  0.366  0.735  1.0
  O  O31  1  0.750  0.911  0.199  1.0
  O  O32  1  0.992  0.366  0.735  1.0
  O  O33  1  0.512  0.343  0.097  1.0
  O  O34  1  0.750  0.220  0.448  1.0
  O  O35  1  0.488  0.843  0.403  1.0
  O  O36  1  0.750  0.280  0.948  1.0
  O  O37  1  0.250  0.411  0.301  1.0
  O  O38  1  0.250  0.611  0.416  1.0
  O  O39  1  0.012  0.843  0.403  1.0
  O  O40  1  0.988  0.157  0.597  1.0
  O  O41  1  0.750  0.389  0.584  1.0
  O  O42  1  0.008  0.866  0.765  1.0
  O  O43  1  0.488  0.657  0.903  1.0
  O  O44  1  0.492  0.634  0.265  1.0
  O  O45  1  0.012  0.657  0.903  1.0
  O  O46  1  0.492  0.866  0.765  1.0
  O  O47  1  0.750  0.111  0.084  1.0
[/CIF]
.
The structure described by K2CuP2O7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(3), and four equivalent O(5) atoms. In the second K site, K(2) is bonded in a 9-coordinate geometry to one O(1), two equivalent O(2), two equivalent O(5), and four equivalent O(3) atoms. Cu(1) is bonded to one O(1), two equivalent O(3), and two equivalent O(5) atoms to form CuO5 square pyramids that share corners with two 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(2), one O(4), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(2)O4 tetrahedra. In the second P site, P(2) is bonded to one O(1), one O(4), and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with three equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(1)O4 tetrahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), one Cu(1), and one P(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one P(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one K(1), two equivalent K(2), one Cu(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one K(2), two equivalent K(1), one Cu(1), and one P(2) atom. is represented by the CIF card [CIF]
data_K2CuP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.260
_cell_length_b   9.486
_cell_length_c   14.174
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   707.201
_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
  K  K0  1  0.750  0.376  0.299  1.0
  K  K1  1  0.250  0.624  0.701  1.0
  K  K2  1  0.750  0.630  0.090  1.0
  K  K3  1  0.750  0.870  0.590  1.0
  K  K4  1  0.750  0.124  0.799  1.0
  K  K5  1  0.250  0.876  0.201  1.0
  K  K6  1  0.250  0.370  0.910  1.0
  K  K7  1  0.250  0.130  0.410  1.0
  Cu  Cu8  1  0.250  0.251  0.170  1.0
  Cu  Cu9  1  0.250  0.249  0.670  1.0
  Cu  Cu10  1  0.750  0.749  0.830  1.0
  Cu  Cu11  1  0.750  0.751  0.330  1.0
  P  P12  1  0.250  0.724  0.947  1.0
  P  P13  1  0.250  0.776  0.447  1.0
  P  P14  1  0.750  0.068  0.194  1.0
  P  P15  1  0.250  0.568  0.306  1.0
  P  P16  1  0.750  0.224  0.553  1.0
  P  P17  1  0.750  0.276  0.053  1.0
  P  P18  1  0.250  0.932  0.806  1.0
  P  P19  1  0.750  0.432  0.694  1.0
  O  O20  1  0.750  0.589  0.699  1.0
  O  O21  1  0.250  0.720  0.052  1.0
  O  O22  1  0.512  0.157  0.597  1.0
  O  O23  1  0.250  0.889  0.916  1.0
  O  O24  1  0.250  0.089  0.801  1.0
  O  O25  1  0.992  0.134  0.235  1.0
  O  O26  1  0.508  0.134  0.235  1.0
  O  O27  1  0.008  0.634  0.265  1.0
  O  O28  1  0.988  0.343  0.097  1.0
  O  O29  1  0.250  0.780  0.552  1.0
  O  O30  1  0.508  0.366  0.735  1.0
  O  O31  1  0.750  0.911  0.199  1.0
  O  O32  1  0.992  0.366  0.735  1.0
  O  O33  1  0.512  0.343  0.097  1.0
  O  O34  1  0.750  0.220  0.448  1.0
  O  O35  1  0.488  0.843  0.403  1.0
  O  O36  1  0.750  0.280  0.948  1.0
  O  O37  1  0.250  0.411  0.301  1.0
  O  O38  1  0.250  0.611  0.416  1.0
  O  O39  1  0.012  0.843  0.403  1.0
  O  O40  1  0.988  0.157  0.597  1.0
  O  O41  1  0.750  0.389  0.584  1.0
  O  O42  1  0.008  0.866  0.765  1.0
  O  O43  1  0.488  0.657  0.903  1.0
  O  O44  1  0.492  0.634  0.265  1.0
  O  O45  1  0.012  0.657  0.903  1.0
  O  O46  1  0.492  0.866  0.765  1.0
  O  O47  1  0.750  0.111  0.084  1.0
[/CIF]
.