The crystal structure described by SiP2O7 crystallizes in the monoclinic P2_1/c space group. Si(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(7) atom to form SiO6 octahedra that share corners with three 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(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Si(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-41°. In the second P site, P(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom 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 range from 24-40°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. In the second O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. In the third O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. is represented by the CIF file [CIF]
data_SiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.325
_cell_length_b   4.742
_cell_length_c   14.747
_cell_angle_alpha   89.900
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   442.260
_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
  Si  Si0  1  0.917  0.750  0.135  1.0
  Si  Si1  1  0.417  0.250  0.365  1.0
  Si  Si2  1  0.083  0.250  0.865  1.0
  Si  Si3  1  0.583  0.750  0.635  1.0
  P  P4  1  0.309  0.254  0.573  1.0
  P  P5  1  0.809  0.746  0.927  1.0
  P  P6  1  0.691  0.746  0.427  1.0
  P  P7  1  0.191  0.254  0.073  1.0
  P  P8  1  0.605  0.262  0.168  1.0
  P  P9  1  0.105  0.738  0.332  1.0
  P  P10  1  0.395  0.738  0.832  1.0
  P  P11  1  0.895  0.262  0.668  1.0
  O  O12  1  0.008  0.165  0.753  1.0
  O  O13  1  0.508  0.835  0.747  1.0
  O  O14  1  0.992  0.835  0.247  1.0
  O  O15  1  0.492  0.165  0.253  1.0
  O  O16  1  0.795  0.548  0.679  1.0
  O  O17  1  0.295  0.452  0.821  1.0
  O  O18  1  0.205  0.452  0.321  1.0
  O  O19  1  0.705  0.548  0.179  1.0
  O  O20  1  0.743  0.047  0.632  1.0
  O  O21  1  0.243  0.953  0.868  1.0
  O  O22  1  0.257  0.953  0.368  1.0
  O  O23  1  0.757  0.047  0.132  1.0
  O  O24  1  0.436  0.288  0.090  1.0
  O  O25  1  0.936  0.712  0.410  1.0
  O  O26  1  0.564  0.712  0.910  1.0
  O  O27  1  0.064  0.288  0.590  1.0
  O  O28  1  0.168  0.337  0.975  1.0
  O  O29  1  0.668  0.663  0.525  1.0
  O  O30  1  0.832  0.663  0.025  1.0
  O  O31  1  0.332  0.337  0.475  1.0
  O  O32  1  0.082  0.455  0.137  1.0
  O  O33  1  0.582  0.545  0.363  1.0
  O  O34  1  0.918  0.545  0.863  1.0
  O  O35  1  0.418  0.455  0.637  1.0
  O  O36  1  0.134  0.950  0.092  1.0
  O  O37  1  0.634  0.050  0.408  1.0
  O  O38  1  0.866  0.050  0.908  1.0
  O  O39  1  0.366  0.950  0.592  1.0
[/CIF]
.
The crystal structure described by SiP2O7 crystallizes in the monoclinic P2_1/c space group. Si(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(7) atom to form SiO6 octahedra that share corners with three 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(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Si(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-41°. In the second P site, P(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom 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 range from 24-40°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. In the second O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. In the third O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom. is represented by the CIF file [CIF]
data_SiP2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.325
_cell_length_b   4.742
_cell_length_c   14.747
_cell_angle_alpha   89.900
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   442.260
_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
  Si  Si0  1  0.917  0.750  0.135  1.0
  Si  Si1  1  0.417  0.250  0.365  1.0
  Si  Si2  1  0.083  0.250  0.865  1.0
  Si  Si3  1  0.583  0.750  0.635  1.0
  P  P4  1  0.309  0.254  0.573  1.0
  P  P5  1  0.809  0.746  0.927  1.0
  P  P6  1  0.691  0.746  0.427  1.0
  P  P7  1  0.191  0.254  0.073  1.0
  P  P8  1  0.605  0.262  0.168  1.0
  P  P9  1  0.105  0.738  0.332  1.0
  P  P10  1  0.395  0.738  0.832  1.0
  P  P11  1  0.895  0.262  0.668  1.0
  O  O12  1  0.008  0.165  0.753  1.0
  O  O13  1  0.508  0.835  0.747  1.0
  O  O14  1  0.992  0.835  0.247  1.0
  O  O15  1  0.492  0.165  0.253  1.0
  O  O16  1  0.795  0.548  0.679  1.0
  O  O17  1  0.295  0.452  0.821  1.0
  O  O18  1  0.205  0.452  0.321  1.0
  O  O19  1  0.705  0.548  0.179  1.0
  O  O20  1  0.743  0.047  0.632  1.0
  O  O21  1  0.243  0.953  0.868  1.0
  O  O22  1  0.257  0.953  0.368  1.0
  O  O23  1  0.757  0.047  0.132  1.0
  O  O24  1  0.436  0.288  0.090  1.0
  O  O25  1  0.936  0.712  0.410  1.0
  O  O26  1  0.564  0.712  0.910  1.0
  O  O27  1  0.064  0.288  0.590  1.0
  O  O28  1  0.168  0.337  0.975  1.0
  O  O29  1  0.668  0.663  0.525  1.0
  O  O30  1  0.832  0.663  0.025  1.0
  O  O31  1  0.332  0.337  0.475  1.0
  O  O32  1  0.082  0.455  0.137  1.0
  O  O33  1  0.582  0.545  0.363  1.0
  O  O34  1  0.918  0.545  0.863  1.0
  O  O35  1  0.418  0.455  0.637  1.0
  O  O36  1  0.134  0.950  0.092  1.0
  O  O37  1  0.634  0.050  0.408  1.0
  O  O38  1  0.866  0.050  0.908  1.0
  O  O39  1  0.366  0.950  0.592  1.0
[/CIF]
.