The crystal structure described by K4P2O7 crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to nine equivalent O(1) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. In the third K site, K(3) is bonded to six equivalent O(1) atoms to form KO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(2) and three equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent K(3)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 25°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(2), one K(3), three equivalent K(1), and one P(1) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent P(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_K4P2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.904
_cell_length_b   5.904
_cell_length_c   14.860
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   448.600
_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
  K  K0  1  0.333  0.667  0.920  1.0
  K  K1  1  0.667  0.333  0.080  1.0
  K  K2  1  0.667  0.333  0.420  1.0
  K  K3  1  0.333  0.667  0.580  1.0
  K  K4  1  0.000  1.000  0.250  1.0
  K  K5  1  1.000  0.000  0.750  1.0
  K  K6  1  1.000  0.000  1.000  1.0
  K  K7  1  1.000  0.000  0.500  1.0
  P  P8  1  0.333  0.667  0.142  1.0
  P  P9  1  0.667  0.333  0.858  1.0
  P  P10  1  0.667  0.333  0.642  1.0
  P  P11  1  0.333  0.667  0.358  1.0
  O  O12  1  0.191  0.809  0.114  1.0
  O  O13  1  0.191  0.382  0.114  1.0
  O  O14  1  0.618  0.809  0.114  1.0
  O  O15  1  0.809  0.191  0.886  1.0
  O  O16  1  0.809  0.618  0.886  1.0
  O  O17  1  0.382  0.191  0.886  1.0
  O  O18  1  0.809  0.191  0.614  1.0
  O  O19  1  0.809  0.618  0.614  1.0
  O  O20  1  0.382  0.191  0.614  1.0
  O  O21  1  0.191  0.809  0.386  1.0
  O  O22  1  0.191  0.382  0.386  1.0
  O  O23  1  0.618  0.809  0.386  1.0
  O  O24  1  0.333  0.667  0.250  1.0
  O  O25  1  0.667  0.333  0.750  1.0
[/CIF]
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The crystal structure described by K4P2O7 crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to nine equivalent O(1) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. In the third K site, K(3) is bonded to six equivalent O(1) atoms to form KO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(2) and three equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent K(3)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 25°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(2), one K(3), three equivalent K(1), and one P(1) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent P(1) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_K4P2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.904
_cell_length_b   5.904
_cell_length_c   14.860
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   448.600
_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
  K  K0  1  0.333  0.667  0.920  1.0
  K  K1  1  0.667  0.333  0.080  1.0
  K  K2  1  0.667  0.333  0.420  1.0
  K  K3  1  0.333  0.667  0.580  1.0
  K  K4  1  0.000  1.000  0.250  1.0
  K  K5  1  1.000  0.000  0.750  1.0
  K  K6  1  1.000  0.000  1.000  1.0
  K  K7  1  1.000  0.000  0.500  1.0
  P  P8  1  0.333  0.667  0.142  1.0
  P  P9  1  0.667  0.333  0.858  1.0
  P  P10  1  0.667  0.333  0.642  1.0
  P  P11  1  0.333  0.667  0.358  1.0
  O  O12  1  0.191  0.809  0.114  1.0
  O  O13  1  0.191  0.382  0.114  1.0
  O  O14  1  0.618  0.809  0.114  1.0
  O  O15  1  0.809  0.191  0.886  1.0
  O  O16  1  0.809  0.618  0.886  1.0
  O  O17  1  0.382  0.191  0.886  1.0
  O  O18  1  0.809  0.191  0.614  1.0
  O  O19  1  0.809  0.618  0.614  1.0
  O  O20  1  0.382  0.191  0.614  1.0
  O  O21  1  0.191  0.809  0.386  1.0
  O  O22  1  0.191  0.382  0.386  1.0
  O  O23  1  0.618  0.809  0.386  1.0
  O  O24  1  0.333  0.667  0.250  1.0
  O  O25  1  0.667  0.333  0.750  1.0
[/CIF]
.