The compound described by WSi2O7 crystallizes in the monoclinic C2/c space group. There are two inequivalent W sites. In the first W site, W(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent W(2)O6 octahedra. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent W(1)O6 octahedra. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-57°. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(7) is bonded in a single-bond geometry to one Si(1) atom. In the third O site, O(1) is bonded in a distorted bent 120 degrees geometry to one W(2) and one Si(2) atom. In the fourth O site, O(2) is bonded in a water-like geometry to one W(1) and one W(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one W(1) and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one W(1), one W(2), and one Si(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Si2WO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.483
_cell_length_b   9.483
_cell_length_c   10.385
_cell_angle_alpha   60.393
_cell_angle_beta   60.393
_cell_angle_gamma   49.538
_symmetry_Int_Tables_number   1
_cell_volume   596.217
_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  0.527  0.134  0.659  1.0
  Si  Si1  1  0.134  0.527  0.159  1.0
  Si  Si2  1  0.534  0.190  0.110  1.0
  Si  Si3  1  0.190  0.534  0.610  1.0
  Si  Si4  1  0.866  0.473  0.841  1.0
  Si  Si5  1  0.466  0.810  0.890  1.0
  Si  Si6  1  0.810  0.466  0.390  1.0
  Si  Si7  1  0.473  0.866  0.341  1.0
  W  W8  1  0.794  0.206  0.750  1.0
  W  W9  1  0.206  0.794  0.250  1.0
  W  W10  1  0.000  0.000  0.000  1.0
  W  W11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.887  0.260  0.374  1.0
  O  O13  1  0.955  0.922  0.394  1.0
  O  O14  1  0.428  0.733  0.085  1.0
  O  O15  1  0.922  0.955  0.894  1.0
  O  O16  1  0.258  0.908  0.334  1.0
  O  O17  1  0.012  0.510  0.672  1.0
  O  O18  1  0.733  0.428  0.585  1.0
  O  O19  1  0.092  0.742  0.166  1.0
  O  O20  1  0.988  0.490  0.328  1.0
  O  O21  1  0.629  0.644  0.319  1.0
  O  O22  1  0.045  0.078  0.606  1.0
  O  O23  1  0.742  0.092  0.666  1.0
  O  O24  1  0.490  0.988  0.828  1.0
  O  O25  1  0.260  0.887  0.874  1.0
  O  O26  1  0.644  0.629  0.819  1.0
  O  O27  1  0.908  0.258  0.834  1.0
  O  O28  1  0.896  0.430  0.992  1.0
  O  O29  1  0.371  0.356  0.681  1.0
  O  O30  1  0.570  0.104  0.508  1.0
  O  O31  1  0.356  0.371  0.181  1.0
  O  O32  1  0.510  0.012  0.172  1.0
  O  O33  1  0.078  0.045  0.106  1.0
  O  O34  1  0.430  0.896  0.492  1.0
  O  O35  1  0.572  0.267  0.915  1.0
  O  O36  1  0.104  0.570  0.008  1.0
  O  O37  1  0.267  0.572  0.415  1.0
  O  O38  1  0.740  0.113  0.126  1.0
  O  O39  1  0.113  0.740  0.626  1.0
[/CIF]
.
The compound described by WSi2O7 crystallizes in the monoclinic C2/c space group. There are two inequivalent W sites. In the first W site, W(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent W(2)O6 octahedra. In the second W site, W(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form WO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent W(1)O6 octahedra. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-57°. 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 W(1)O6 octahedra,  a cornercorner with one W(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(7) is bonded in a single-bond geometry to one Si(1) atom. In the third O site, O(1) is bonded in a distorted bent 120 degrees geometry to one W(2) and one Si(2) atom. In the fourth O site, O(2) is bonded in a water-like geometry to one W(1) and one W(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one W(1) and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one W(1), one W(2), and one Si(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Si2WO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.483
_cell_length_b   9.483
_cell_length_c   10.385
_cell_angle_alpha   60.393
_cell_angle_beta   60.393
_cell_angle_gamma   49.538
_symmetry_Int_Tables_number   1
_cell_volume   596.217
_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  0.527  0.134  0.659  1.0
  Si  Si1  1  0.134  0.527  0.159  1.0
  Si  Si2  1  0.534  0.190  0.110  1.0
  Si  Si3  1  0.190  0.534  0.610  1.0
  Si  Si4  1  0.866  0.473  0.841  1.0
  Si  Si5  1  0.466  0.810  0.890  1.0
  Si  Si6  1  0.810  0.466  0.390  1.0
  Si  Si7  1  0.473  0.866  0.341  1.0
  W  W8  1  0.794  0.206  0.750  1.0
  W  W9  1  0.206  0.794  0.250  1.0
  W  W10  1  0.000  0.000  0.000  1.0
  W  W11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.887  0.260  0.374  1.0
  O  O13  1  0.955  0.922  0.394  1.0
  O  O14  1  0.428  0.733  0.085  1.0
  O  O15  1  0.922  0.955  0.894  1.0
  O  O16  1  0.258  0.908  0.334  1.0
  O  O17  1  0.012  0.510  0.672  1.0
  O  O18  1  0.733  0.428  0.585  1.0
  O  O19  1  0.092  0.742  0.166  1.0
  O  O20  1  0.988  0.490  0.328  1.0
  O  O21  1  0.629  0.644  0.319  1.0
  O  O22  1  0.045  0.078  0.606  1.0
  O  O23  1  0.742  0.092  0.666  1.0
  O  O24  1  0.490  0.988  0.828  1.0
  O  O25  1  0.260  0.887  0.874  1.0
  O  O26  1  0.644  0.629  0.819  1.0
  O  O27  1  0.908  0.258  0.834  1.0
  O  O28  1  0.896  0.430  0.992  1.0
  O  O29  1  0.371  0.356  0.681  1.0
  O  O30  1  0.570  0.104  0.508  1.0
  O  O31  1  0.356  0.371  0.181  1.0
  O  O32  1  0.510  0.012  0.172  1.0
  O  O33  1  0.078  0.045  0.106  1.0
  O  O34  1  0.430  0.896  0.492  1.0
  O  O35  1  0.572  0.267  0.915  1.0
  O  O36  1  0.104  0.570  0.008  1.0
  O  O37  1  0.267  0.572  0.415  1.0
  O  O38  1  0.740  0.113  0.126  1.0
  O  O39  1  0.113  0.740  0.626  1.0
[/CIF]
.