The material structure described by Y2Hf2O7 crystallizes in the monoclinic C2/m space group. Y(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted YO6 pentagonal pyramids that share corners with four equivalent Hf(1)O5 trigonal bipyramids, edges with three equivalent Y(1)O6 pentagonal pyramids, and edges with two equivalent Hf(1)O5 trigonal bipyramids. Hf(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted HfO5 trigonal bipyramids that share corners with four equivalent Y(1)O6 pentagonal pyramids,  a cornercorner with one Hf(1)O5 trigonal bipyramid, edges with two equivalent Y(1)O6 pentagonal pyramids, and  an edgeedge with one Hf(1)O5 trigonal bipyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Y(1) and one Hf(1) atom. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Hf(1) atoms to form distorted edge-sharing OY2Hf2 trigonal pyramids. In the third O site, O(3) is bonded in a linear geometry to two equivalent Hf(1) atoms. is represented by the CIF card [CIF]
data_Y2Hf2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.917
_cell_length_b   5.917
_cell_length_c   5.575
_cell_angle_alpha   84.117
_cell_angle_beta   84.117
_cell_angle_gamma   108.678
_symmetry_Int_Tables_number   1
_cell_volume   182.046
_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
  Y  Y0  1  0.691  0.309  0.000  1.0
  Y  Y1  1  0.309  0.691  0.000  1.0
  Hf  Hf2  1  0.744  0.744  0.397  1.0
  Hf  Hf3  1  0.256  0.256  0.603  1.0
  O  O4  1  0.940  0.597  0.200  1.0
  O  O5  1  0.597  0.940  0.200  1.0
  O  O6  1  0.559  0.559  0.727  1.0
  O  O7  1  0.000  0.000  0.500  1.0
  O  O8  1  0.441  0.441  0.273  1.0
  O  O9  1  0.403  0.060  0.800  1.0
  O  O10  1  0.060  0.403  0.800  1.0
[/CIF]
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The material structure described by Y2Hf2O7 crystallizes in the monoclinic C2/m space group. Y(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted YO6 pentagonal pyramids that share corners with four equivalent Hf(1)O5 trigonal bipyramids, edges with three equivalent Y(1)O6 pentagonal pyramids, and edges with two equivalent Hf(1)O5 trigonal bipyramids. Hf(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted HfO5 trigonal bipyramids that share corners with four equivalent Y(1)O6 pentagonal pyramids,  a cornercorner with one Hf(1)O5 trigonal bipyramid, edges with two equivalent Y(1)O6 pentagonal pyramids, and  an edgeedge with one Hf(1)O5 trigonal bipyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Y(1) and one Hf(1) atom. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Hf(1) atoms to form distorted edge-sharing OY2Hf2 trigonal pyramids. In the third O site, O(3) is bonded in a linear geometry to two equivalent Hf(1) atoms. is represented by the CIF card [CIF]
data_Y2Hf2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.917
_cell_length_b   5.917
_cell_length_c   5.575
_cell_angle_alpha   84.117
_cell_angle_beta   84.117
_cell_angle_gamma   108.678
_symmetry_Int_Tables_number   1
_cell_volume   182.046
_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
  Y  Y0  1  0.691  0.309  0.000  1.0
  Y  Y1  1  0.309  0.691  0.000  1.0
  Hf  Hf2  1  0.744  0.744  0.397  1.0
  Hf  Hf3  1  0.256  0.256  0.603  1.0
  O  O4  1  0.940  0.597  0.200  1.0
  O  O5  1  0.597  0.940  0.200  1.0
  O  O6  1  0.559  0.559  0.727  1.0
  O  O7  1  0.000  0.000  0.500  1.0
  O  O8  1  0.441  0.441  0.273  1.0
  O  O9  1  0.403  0.060  0.800  1.0
  O  O10  1  0.060  0.403  0.800  1.0
[/CIF]
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