The crystal structure described by Sn2Si2O7 crystallizes in the triclinic P-1 space group. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one O(1), one O(11), one O(2), one O(4), one O(6), and one O(9) atom to form SnO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and corners with three equivalent Si(2)O4 tetrahedra. In the second Sn site, Sn(2) is bonded in a 5-coordinate geometry to one O(1), one O(12), one O(14), one O(3), and one O(4) atom. In the third Sn site, Sn(3) is bonded in a 4-coordinate geometry to one O(10), one O(11), one O(12), and one O(2) atom. In the fourth Sn site, Sn(4) is bonded to one O(10), one O(13), one O(14), one O(3), one O(5), and one O(7) atom to form SnO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with three equivalent Si(3)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(1)O6 octahedra, corners with two equivalent Sn(4)O6 octahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 29-54°. In the second Si site, Si(2) is bonded to one O(1), one O(10), one O(2), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(4)O6 octahedra and corners with three equivalent Sn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-49°. In the third Si site, Si(3) is bonded to one O(13), one O(14), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with three equivalent Sn(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-59°. In the fourth Si site, Si(4) is bonded to one O(11), one O(12), one O(13), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(4)O6 octahedra, corners with two equivalent Sn(1)O6 octahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 37-63°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(2), and one Si(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(3), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Sn(2), one Sn(4), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Sn(1), one Sn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Sn(4) and one Si(3) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Sn(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Sn(4) and one Si(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Sn(1) and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Sn(3), one Sn(4), and one Si(2) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(3), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Sn(2), one Sn(3), and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a trigonal planar geometry to one Sn(4), one Si(3), and one Si(4) atom. In the fourteenth O site, O(14) is bonded in a 2-coordinate geometry to one Sn(2), one Sn(4), and one Si(3) atom. is represented by the CIF card [CIF]
data_Si2Sn2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.684
_cell_length_b   6.789
_cell_length_c   12.883
_cell_angle_alpha   80.989
_cell_angle_beta   85.384
_cell_angle_gamma   82.871
_symmetry_Int_Tables_number   1
_cell_volume   571.820
_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  0.858  0.618  0.627  1.0
  Si  Si1  1  0.925  0.196  0.129  1.0
  Si  Si2  1  0.643  0.717  0.426  1.0
  Si  Si3  1  0.556  0.695  0.199  1.0
  Si  Si4  1  0.444  0.305  0.801  1.0
  Si  Si5  1  0.357  0.283  0.574  1.0
  Si  Si6  1  0.075  0.804  0.871  1.0
  Si  Si7  1  0.142  0.382  0.373  1.0
  Sn  Sn8  1  0.926  0.328  0.861  1.0
  Sn  Sn9  1  0.848  0.089  0.652  1.0
  Sn  Sn10  1  0.572  0.777  0.888  1.0
  Sn  Sn11  1  0.651  0.233  0.359  1.0
  Sn  Sn12  1  0.349  0.767  0.641  1.0
  Sn  Sn13  1  0.428  0.223  0.112  1.0
  Sn  Sn14  1  0.152  0.911  0.348  1.0
  Sn  Sn15  1  0.074  0.672  0.139  1.0
  O  O16  1  0.036  0.973  0.179  1.0
  O  O17  1  0.915  0.640  0.863  1.0
  O  O18  1  0.953  0.251  0.374  1.0
  O  O19  1  0.909  0.394  0.696  1.0
  O  O20  1  0.726  0.930  0.380  1.0
  O  O21  1  0.856  0.208  0.010  1.0
  O  O22  1  0.653  0.748  0.676  1.0
  O  O23  1  0.807  0.592  0.507  1.0
  O  O24  1  0.768  0.697  0.129  1.0
  O  O25  1  0.710  0.246  0.199  1.0
  O  O26  1  0.603  0.423  0.854  1.0
  O  O27  1  0.563  0.091  0.777  1.0
  O  O28  1  0.615  0.580  0.328  1.0
  O  O29  1  0.578  0.258  0.512  1.0
  O  O30  1  0.422  0.742  0.488  1.0
  O  O31  1  0.385  0.420  0.672  1.0
  O  O32  1  0.437  0.909  0.223  1.0
  O  O33  1  0.397  0.577  0.146  1.0
  O  O34  1  0.290  0.754  0.801  1.0
  O  O35  1  0.232  0.303  0.871  1.0
  O  O36  1  0.193  0.408  0.493  1.0
  O  O37  1  0.347  0.252  0.324  1.0
  O  O38  1  0.144  0.792  0.990  1.0
  O  O39  1  0.274  0.070  0.620  1.0
  O  O40  1  0.091  0.606  0.304  1.0
  O  O41  1  0.047  0.749  0.626  1.0
  O  O42  1  0.085  0.360  0.137  1.0
  O  O43  1  0.964  0.027  0.821  1.0
[/CIF]
.
The crystal structure described by Sn2Si2O7 crystallizes in the triclinic P-1 space group. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one O(1), one O(11), one O(2), one O(4), one O(6), and one O(9) atom to form SnO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and corners with three equivalent Si(2)O4 tetrahedra. In the second Sn site, Sn(2) is bonded in a 5-coordinate geometry to one O(1), one O(12), one O(14), one O(3), and one O(4) atom. In the third Sn site, Sn(3) is bonded in a 4-coordinate geometry to one O(10), one O(11), one O(12), and one O(2) atom. In the fourth Sn site, Sn(4) is bonded to one O(10), one O(13), one O(14), one O(3), one O(5), and one O(7) atom to form SnO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with three equivalent Si(3)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(1)O6 octahedra, corners with two equivalent Sn(4)O6 octahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 29-54°. In the second Si site, Si(2) is bonded to one O(1), one O(10), one O(2), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(4)O6 octahedra and corners with three equivalent Sn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-49°. In the third Si site, Si(3) is bonded to one O(13), one O(14), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with three equivalent Sn(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-59°. In the fourth Si site, Si(4) is bonded to one O(11), one O(12), one O(13), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(4)O6 octahedra, corners with two equivalent Sn(1)O6 octahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 37-63°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(2), and one Si(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(3), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Sn(2), one Sn(4), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Sn(1), one Sn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Sn(4) and one Si(3) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Sn(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Sn(4) and one Si(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Sn(1) and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Sn(3), one Sn(4), and one Si(2) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(3), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Sn(2), one Sn(3), and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a trigonal planar geometry to one Sn(4), one Si(3), and one Si(4) atom. In the fourteenth O site, O(14) is bonded in a 2-coordinate geometry to one Sn(2), one Sn(4), and one Si(3) atom. is represented by the CIF card [CIF]
data_Si2Sn2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.684
_cell_length_b   6.789
_cell_length_c   12.883
_cell_angle_alpha   80.989
_cell_angle_beta   85.384
_cell_angle_gamma   82.871
_symmetry_Int_Tables_number   1
_cell_volume   571.820
_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  0.858  0.618  0.627  1.0
  Si  Si1  1  0.925  0.196  0.129  1.0
  Si  Si2  1  0.643  0.717  0.426  1.0
  Si  Si3  1  0.556  0.695  0.199  1.0
  Si  Si4  1  0.444  0.305  0.801  1.0
  Si  Si5  1  0.357  0.283  0.574  1.0
  Si  Si6  1  0.075  0.804  0.871  1.0
  Si  Si7  1  0.142  0.382  0.373  1.0
  Sn  Sn8  1  0.926  0.328  0.861  1.0
  Sn  Sn9  1  0.848  0.089  0.652  1.0
  Sn  Sn10  1  0.572  0.777  0.888  1.0
  Sn  Sn11  1  0.651  0.233  0.359  1.0
  Sn  Sn12  1  0.349  0.767  0.641  1.0
  Sn  Sn13  1  0.428  0.223  0.112  1.0
  Sn  Sn14  1  0.152  0.911  0.348  1.0
  Sn  Sn15  1  0.074  0.672  0.139  1.0
  O  O16  1  0.036  0.973  0.179  1.0
  O  O17  1  0.915  0.640  0.863  1.0
  O  O18  1  0.953  0.251  0.374  1.0
  O  O19  1  0.909  0.394  0.696  1.0
  O  O20  1  0.726  0.930  0.380  1.0
  O  O21  1  0.856  0.208  0.010  1.0
  O  O22  1  0.653  0.748  0.676  1.0
  O  O23  1  0.807  0.592  0.507  1.0
  O  O24  1  0.768  0.697  0.129  1.0
  O  O25  1  0.710  0.246  0.199  1.0
  O  O26  1  0.603  0.423  0.854  1.0
  O  O27  1  0.563  0.091  0.777  1.0
  O  O28  1  0.615  0.580  0.328  1.0
  O  O29  1  0.578  0.258  0.512  1.0
  O  O30  1  0.422  0.742  0.488  1.0
  O  O31  1  0.385  0.420  0.672  1.0
  O  O32  1  0.437  0.909  0.223  1.0
  O  O33  1  0.397  0.577  0.146  1.0
  O  O34  1  0.290  0.754  0.801  1.0
  O  O35  1  0.232  0.303  0.871  1.0
  O  O36  1  0.193  0.408  0.493  1.0
  O  O37  1  0.347  0.252  0.324  1.0
  O  O38  1  0.144  0.792  0.990  1.0
  O  O39  1  0.274  0.070  0.620  1.0
  O  O40  1  0.091  0.606  0.304  1.0
  O  O41  1  0.047  0.749  0.626  1.0
  O  O42  1  0.085  0.360  0.137  1.0
  O  O43  1  0.964  0.027  0.821  1.0
[/CIF]
.