The structure described by Ca3Si4(SnO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(2), one O(3), one O(6), two equivalent O(5), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(4) atoms. In the second Sn site, Sn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form SnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(2), one Sn(2), and one Si(2) atom. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Sn(1), and one Sn(2) atom to form a mixture of distorted corner and edge-sharing OCa2Sn2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one Si(1) atom. is represented by the CIF card [CIF]
data_Ca3Si4(SnO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.529
_cell_length_b   10.925
_cell_length_c   9.077
_cell_angle_alpha   69.822
_cell_angle_beta   65.498
_cell_angle_gamma   69.844
_symmetry_Int_Tables_number   1
_cell_volume   619.664
_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
  Ca  Ca0  1  0.783  0.004  0.467  1.0
  Ca  Ca1  1  0.253  0.496  0.033  1.0
  Ca  Ca2  1  0.747  0.504  0.967  1.0
  Ca  Ca3  1  0.684  0.250  0.750  1.0
  Ca  Ca4  1  0.217  0.996  0.533  1.0
  Ca  Ca5  1  0.316  0.750  0.250  1.0
  Si  Si6  1  0.459  0.292  0.318  1.0
  Si  Si7  1  0.931  0.792  0.818  1.0
  Si  Si8  1  0.513  0.922  0.827  1.0
  Si  Si9  1  0.738  0.422  0.327  1.0
  Si  Si10  1  0.069  0.208  0.182  1.0
  Si  Si11  1  0.487  0.078  0.173  1.0
  Si  Si12  1  0.262  0.578  0.673  1.0
  Si  Si13  1  0.541  0.708  0.682  1.0
  Sn  Sn14  1  0.195  0.250  0.750  1.0
  Sn  Sn15  1  0.805  0.750  0.250  1.0
  Sn  Sn16  1  0.000  0.000  0.000  1.0
  Sn  Sn17  1  0.000  0.500  0.500  1.0
  O  O18  1  0.206  0.583  0.515  1.0
  O  O19  1  0.083  0.603  0.257  1.0
  O  O20  1  0.414  0.940  0.269  1.0
  O  O21  1  0.057  0.103  0.757  1.0
  O  O22  1  0.771  0.674  0.552  1.0
  O  O23  1  0.957  0.373  0.172  1.0
  O  O24  1  0.376  0.440  0.769  1.0
  O  O25  1  0.997  0.826  0.948  1.0
  O  O26  1  0.043  0.627  0.828  1.0
  O  O27  1  0.381  0.703  0.603  1.0
  O  O28  1  0.917  0.397  0.743  1.0
  O  O29  1  0.229  0.326  0.448  1.0
  O  O30  1  0.502  0.127  0.328  1.0
  O  O31  1  0.695  0.083  0.015  1.0
  O  O32  1  0.314  0.203  0.103  1.0
  O  O33  1  0.003  0.174  0.052  1.0
  O  O34  1  0.013  0.123  0.372  1.0
  O  O35  1  0.619  0.297  0.397  1.0
  O  O36  1  0.507  0.377  0.128  1.0
  O  O37  1  0.686  0.797  0.897  1.0
  O  O38  1  0.498  0.873  0.672  1.0
  O  O39  1  0.943  0.897  0.243  1.0
  O  O40  1  0.493  0.623  0.872  1.0
  O  O41  1  0.586  0.060  0.731  1.0
  O  O42  1  0.987  0.877  0.628  1.0
  O  O43  1  0.624  0.560  0.231  1.0
  O  O44  1  0.305  0.917  0.985  1.0
  O  O45  1  0.794  0.417  0.485  1.0
[/CIF]
.
The structure described by Ca3Si4(SnO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(2), one O(3), one O(6), two equivalent O(5), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(4) atoms. In the second Sn site, Sn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form SnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(2), one Sn(2), and one Si(2) atom. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Sn(1), and one Sn(2) atom to form a mixture of distorted corner and edge-sharing OCa2Sn2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Sn(1), one Sn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one Si(1) atom. is represented by the CIF card [CIF]
data_Ca3Si4(SnO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.529
_cell_length_b   10.925
_cell_length_c   9.077
_cell_angle_alpha   69.822
_cell_angle_beta   65.498
_cell_angle_gamma   69.844
_symmetry_Int_Tables_number   1
_cell_volume   619.664
_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
  Ca  Ca0  1  0.783  0.004  0.467  1.0
  Ca  Ca1  1  0.253  0.496  0.033  1.0
  Ca  Ca2  1  0.747  0.504  0.967  1.0
  Ca  Ca3  1  0.684  0.250  0.750  1.0
  Ca  Ca4  1  0.217  0.996  0.533  1.0
  Ca  Ca5  1  0.316  0.750  0.250  1.0
  Si  Si6  1  0.459  0.292  0.318  1.0
  Si  Si7  1  0.931  0.792  0.818  1.0
  Si  Si8  1  0.513  0.922  0.827  1.0
  Si  Si9  1  0.738  0.422  0.327  1.0
  Si  Si10  1  0.069  0.208  0.182  1.0
  Si  Si11  1  0.487  0.078  0.173  1.0
  Si  Si12  1  0.262  0.578  0.673  1.0
  Si  Si13  1  0.541  0.708  0.682  1.0
  Sn  Sn14  1  0.195  0.250  0.750  1.0
  Sn  Sn15  1  0.805  0.750  0.250  1.0
  Sn  Sn16  1  0.000  0.000  0.000  1.0
  Sn  Sn17  1  0.000  0.500  0.500  1.0
  O  O18  1  0.206  0.583  0.515  1.0
  O  O19  1  0.083  0.603  0.257  1.0
  O  O20  1  0.414  0.940  0.269  1.0
  O  O21  1  0.057  0.103  0.757  1.0
  O  O22  1  0.771  0.674  0.552  1.0
  O  O23  1  0.957  0.373  0.172  1.0
  O  O24  1  0.376  0.440  0.769  1.0
  O  O25  1  0.997  0.826  0.948  1.0
  O  O26  1  0.043  0.627  0.828  1.0
  O  O27  1  0.381  0.703  0.603  1.0
  O  O28  1  0.917  0.397  0.743  1.0
  O  O29  1  0.229  0.326  0.448  1.0
  O  O30  1  0.502  0.127  0.328  1.0
  O  O31  1  0.695  0.083  0.015  1.0
  O  O32  1  0.314  0.203  0.103  1.0
  O  O33  1  0.003  0.174  0.052  1.0
  O  O34  1  0.013  0.123  0.372  1.0
  O  O35  1  0.619  0.297  0.397  1.0
  O  O36  1  0.507  0.377  0.128  1.0
  O  O37  1  0.686  0.797  0.897  1.0
  O  O38  1  0.498  0.873  0.672  1.0
  O  O39  1  0.943  0.897  0.243  1.0
  O  O40  1  0.493  0.623  0.872  1.0
  O  O41  1  0.586  0.060  0.731  1.0
  O  O42  1  0.987  0.877  0.628  1.0
  O  O43  1  0.624  0.560  0.231  1.0
  O  O44  1  0.305  0.917  0.985  1.0
  O  O45  1  0.794  0.417  0.485  1.0
[/CIF]
.