The crystal structure described by Er2Si2O7 crystallizes in the monoclinic C2/m space group. Er(1) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form distorted ErO6 pentagonal pyramids that share corners with six equivalent Si(1)O4 tetrahedra and edges with three equivalent Er(1)O6 pentagonal pyramids. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with six equivalent Er(1)O6 pentagonal pyramids and  a cornercorner with one Si(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one Si(1) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.597
_cell_length_b   5.597
_cell_length_c   4.723
_cell_angle_alpha   82.758
_cell_angle_beta   82.758
_cell_angle_gamma   105.139
_symmetry_Int_Tables_number   1
_cell_volume   139.709
_cell_formula_units_Z   1
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
  Er  Er0  1  0.307  0.693  0.000  1.0
  Er  Er1  1  0.693  0.307  0.000  1.0
  Si  Si2  1  0.219  0.219  0.588  1.0
  Si  Si3  1  0.781  0.781  0.412  1.0
  O  O4  1  0.914  0.613  0.220  1.0
  O  O5  1  0.387  0.086  0.780  1.0
  O  O6  1  0.086  0.387  0.780  1.0
  O  O7  1  0.613  0.914  0.220  1.0
  O  O8  1  0.000  0.000  0.500  1.0
  O  O9  1  0.617  0.617  0.715  1.0
  O  O10  1  0.383  0.383  0.285  1.0
[/CIF]
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The crystal structure described by Er2Si2O7 crystallizes in the monoclinic C2/m space group. Er(1) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form distorted ErO6 pentagonal pyramids that share corners with six equivalent Si(1)O4 tetrahedra and edges with three equivalent Er(1)O6 pentagonal pyramids. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with six equivalent Er(1)O6 pentagonal pyramids and  a cornercorner with one Si(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one Si(1) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.597
_cell_length_b   5.597
_cell_length_c   4.723
_cell_angle_alpha   82.758
_cell_angle_beta   82.758
_cell_angle_gamma   105.139
_symmetry_Int_Tables_number   1
_cell_volume   139.709
_cell_formula_units_Z   1
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
  Er  Er0  1  0.307  0.693  0.000  1.0
  Er  Er1  1  0.693  0.307  0.000  1.0
  Si  Si2  1  0.219  0.219  0.588  1.0
  Si  Si3  1  0.781  0.781  0.412  1.0
  O  O4  1  0.914  0.613  0.220  1.0
  O  O5  1  0.387  0.086  0.780  1.0
  O  O6  1  0.086  0.387  0.780  1.0
  O  O7  1  0.613  0.914  0.220  1.0
  O  O8  1  0.000  0.000  0.500  1.0
  O  O9  1  0.617  0.617  0.715  1.0
  O  O10  1  0.383  0.383  0.285  1.0
[/CIF]
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