The material structure described by Y2Si2O7 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form distorted YO8 hexagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O6 octahedra, edges with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Si(2)O4 tetrahedra. In the second Y site, Y(2) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form YO6 octahedra that share corners with two equivalent Y(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Y(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with two equivalent Y(1)O8 hexagonal bipyramids, corners with two equivalent Y(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and edges with two equivalent Y(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 45°. In the second Si site, Si(2) is bonded to one O(1), one O(4), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Y(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and edges with two equivalent Y(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 45-61°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Y(1), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to two equivalent Y(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Y(2) and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Si(1) atom. is represented by the CIF file [CIF]
data_Y2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.140
_cell_length_b   5.115
_cell_length_c   7.449
_cell_angle_alpha   72.895
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   296.460
_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
  Y  Y0  1  0.500  0.000  0.000  1.0
  Y  Y1  1  0.000  0.000  0.000  1.0
  Y  Y2  1  0.000  0.500  0.500  1.0
  Y  Y3  1  0.500  0.500  0.500  1.0
  Si  Si4  1  0.250  0.474  0.107  1.0
  Si  Si5  1  0.750  0.101  0.316  1.0
  Si  Si6  1  0.750  0.526  0.893  1.0
  Si  Si7  1  0.250  0.899  0.684  1.0
  O  O8  1  0.250  0.741  0.915  1.0
  O  O9  1  0.250  0.183  0.058  1.0
  O  O10  1  0.417  0.079  0.672  1.0
  O  O11  1  0.250  0.685  0.560  1.0
  O  O12  1  0.920  0.465  0.797  1.0
  O  O13  1  0.750  0.259  0.085  1.0
  O  O14  1  0.917  0.921  0.328  1.0
  O  O15  1  0.750  0.315  0.440  1.0
  O  O16  1  0.750  0.817  0.942  1.0
  O  O17  1  0.080  0.535  0.203  1.0
  O  O18  1  0.583  0.921  0.328  1.0
  O  O19  1  0.580  0.465  0.797  1.0
  O  O20  1  0.083  0.079  0.672  1.0
  O  O21  1  0.420  0.535  0.203  1.0
[/CIF]
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The material structure described by Y2Si2O7 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form distorted YO8 hexagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O6 octahedra, edges with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Si(2)O4 tetrahedra. In the second Y site, Y(2) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form YO6 octahedra that share corners with two equivalent Y(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Y(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with two equivalent Y(1)O8 hexagonal bipyramids, corners with two equivalent Y(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and edges with two equivalent Y(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 45°. In the second Si site, Si(2) is bonded to one O(1), one O(4), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Y(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and edges with two equivalent Y(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 45-61°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Y(1), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to two equivalent Y(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Y(2) and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Si(1) atom. is represented by the CIF file [CIF]
data_Y2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.140
_cell_length_b   5.115
_cell_length_c   7.449
_cell_angle_alpha   72.895
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   296.460
_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
  Y  Y0  1  0.500  0.000  0.000  1.0
  Y  Y1  1  0.000  0.000  0.000  1.0
  Y  Y2  1  0.000  0.500  0.500  1.0
  Y  Y3  1  0.500  0.500  0.500  1.0
  Si  Si4  1  0.250  0.474  0.107  1.0
  Si  Si5  1  0.750  0.101  0.316  1.0
  Si  Si6  1  0.750  0.526  0.893  1.0
  Si  Si7  1  0.250  0.899  0.684  1.0
  O  O8  1  0.250  0.741  0.915  1.0
  O  O9  1  0.250  0.183  0.058  1.0
  O  O10  1  0.417  0.079  0.672  1.0
  O  O11  1  0.250  0.685  0.560  1.0
  O  O12  1  0.920  0.465  0.797  1.0
  O  O13  1  0.750  0.259  0.085  1.0
  O  O14  1  0.917  0.921  0.328  1.0
  O  O15  1  0.750  0.315  0.440  1.0
  O  O16  1  0.750  0.817  0.942  1.0
  O  O17  1  0.080  0.535  0.203  1.0
  O  O18  1  0.583  0.921  0.328  1.0
  O  O19  1  0.580  0.465  0.797  1.0
  O  O20  1  0.083  0.079  0.672  1.0
  O  O21  1  0.420  0.535  0.203  1.0
[/CIF]
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