The crystal structure described by SiP2O7 crystallizes in the hexagonal P6_3/m space group. Si(1) is bonded to six equivalent O(1) atoms to form SiO6 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 Si(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. There are two inequivalent O sites. In the first O site, O(2) is bonded in a linear geometry to two equivalent P(1) atoms. In the second O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. is represented by the CIF card [CIF]
data_SiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.713
_cell_length_b   4.713
_cell_length_c   11.997
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   230.810
_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
  Si  Si0  1  0.000  0.000  0.000  1.0
  Si  Si1  1  1.000  0.000  0.500  1.0
  P  P2  1  0.333  0.667  0.880  1.0
  P  P3  1  0.667  0.333  0.120  1.0
  P  P4  1  0.667  0.333  0.380  1.0
  P  P5  1  0.333  0.667  0.620  1.0
  O  O6  1  0.935  0.265  0.086  1.0
  O  O7  1  0.735  0.670  0.086  1.0
  O  O8  1  0.065  0.735  0.586  1.0
  O  O9  1  0.265  0.330  0.914  1.0
  O  O10  1  0.333  0.667  0.750  1.0
  O  O11  1  0.670  0.935  0.586  1.0
  O  O12  1  0.735  0.670  0.414  1.0
  O  O13  1  0.670  0.935  0.914  1.0
  O  O14  1  0.330  0.065  0.086  1.0
  O  O15  1  0.265  0.330  0.586  1.0
  O  O16  1  0.935  0.265  0.414  1.0
  O  O17  1  0.330  0.065  0.414  1.0
  O  O18  1  0.065  0.735  0.914  1.0
  O  O19  1  0.667  0.333  0.250  1.0
[/CIF]
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The crystal structure described by SiP2O7 crystallizes in the hexagonal P6_3/m space group. Si(1) is bonded to six equivalent O(1) atoms to form SiO6 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 Si(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. There are two inequivalent O sites. In the first O site, O(2) is bonded in a linear geometry to two equivalent P(1) atoms. In the second O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. is represented by the CIF card [CIF]
data_SiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.713
_cell_length_b   4.713
_cell_length_c   11.997
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   230.810
_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
  Si  Si0  1  0.000  0.000  0.000  1.0
  Si  Si1  1  1.000  0.000  0.500  1.0
  P  P2  1  0.333  0.667  0.880  1.0
  P  P3  1  0.667  0.333  0.120  1.0
  P  P4  1  0.667  0.333  0.380  1.0
  P  P5  1  0.333  0.667  0.620  1.0
  O  O6  1  0.935  0.265  0.086  1.0
  O  O7  1  0.735  0.670  0.086  1.0
  O  O8  1  0.065  0.735  0.586  1.0
  O  O9  1  0.265  0.330  0.914  1.0
  O  O10  1  0.333  0.667  0.750  1.0
  O  O11  1  0.670  0.935  0.586  1.0
  O  O12  1  0.735  0.670  0.414  1.0
  O  O13  1  0.670  0.935  0.914  1.0
  O  O14  1  0.330  0.065  0.086  1.0
  O  O15  1  0.265  0.330  0.586  1.0
  O  O16  1  0.935  0.265  0.414  1.0
  O  O17  1  0.330  0.065  0.414  1.0
  O  O18  1  0.065  0.735  0.914  1.0
  O  O19  1  0.667  0.333  0.250  1.0
[/CIF]
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