The material structure described by Y2Hf2O7 crystallizes in the tetragonal P4_12_12 space group. Y(1) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. Hf(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing HfO5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and two equivalent Hf(1) atoms to form distorted OY2Hf2 trigonal pyramids that share corners with two equivalent O(2)Y3Hf tetrahedra, corners with two equivalent O(1)Y2Hf2 trigonal pyramids, edges with three equivalent O(2)Y3Hf tetrahedra, and  an edgeedge with one O(1)Y2Hf2 trigonal pyramid. In the second O site, O(2) is bonded to three equivalent Y(1) and one Hf(1) atom to form distorted OY3Hf tetrahedra that share corners with four equivalent O(2)Y3Hf tetrahedra, corners with two equivalent O(1)Y2Hf2 trigonal pyramids,  an edgeedge with one O(2)Y3Hf tetrahedra, and edges with three equivalent O(1)Y2Hf2 trigonal pyramids. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Y(1) and one Hf(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Hf(1) atoms. is represented by the CIF file [CIF]
data_Y2Hf2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.314
_cell_length_b   7.314
_cell_length_c   12.524
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   669.977
_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
  Y  Y0  1  0.137  0.625  0.134  1.0
  Y  Y1  1  0.125  0.363  0.884  1.0
  Y  Y2  1  0.375  0.863  0.366  1.0
  Y  Y3  1  0.363  0.125  0.116  1.0
  Y  Y4  1  0.637  0.875  0.616  1.0
  Y  Y5  1  0.625  0.137  0.866  1.0
  Y  Y6  1  0.875  0.637  0.384  1.0
  Y  Y7  1  0.863  0.375  0.634  1.0
  Hf  Hf8  1  0.099  0.872  0.595  1.0
  Hf  Hf9  1  0.128  0.901  0.905  1.0
  Hf  Hf10  1  0.372  0.401  0.345  1.0
  Hf  Hf11  1  0.401  0.372  0.655  1.0
  Hf  Hf12  1  0.599  0.628  0.155  1.0
  Hf  Hf13  1  0.628  0.599  0.845  1.0
  Hf  Hf14  1  0.872  0.099  0.405  1.0
  Hf  Hf15  1  0.901  0.128  0.095  1.0
  O  O16  1  0.070  0.909  0.415  1.0
  O  O17  1  0.082  0.326  0.074  1.0
  O  O18  1  0.091  0.930  0.085  1.0
  O  O19  1  0.153  0.640  0.953  1.0
  O  O20  1  0.174  0.582  0.324  1.0
  O  O21  1  0.140  0.347  0.703  1.0
  O  O22  1  0.143  0.857  0.750  1.0
  O  O23  1  0.357  0.357  0.500  1.0
  O  O24  1  0.360  0.847  0.547  1.0
  O  O25  1  0.326  0.082  0.926  1.0
  O  O26  1  0.347  0.140  0.297  1.0
  O  O27  1  0.409  0.430  0.165  1.0
  O  O28  1  0.418  0.826  0.176  1.0
  O  O29  1  0.430  0.409  0.835  1.0
  O  O30  1  0.570  0.591  0.335  1.0
  O  O31  1  0.582  0.174  0.676  1.0
  O  O32  1  0.591  0.570  0.665  1.0
  O  O33  1  0.653  0.860  0.797  1.0
  O  O34  1  0.674  0.918  0.426  1.0
  O  O35  1  0.640  0.153  0.047  1.0
  O  O36  1  0.643  0.643  0.000  1.0
  O  O37  1  0.857  0.143  0.250  1.0
  O  O38  1  0.860  0.653  0.203  1.0
  O  O39  1  0.826  0.418  0.824  1.0
  O  O40  1  0.847  0.360  0.453  1.0
  O  O41  1  0.909  0.070  0.585  1.0
  O  O42  1  0.918  0.674  0.574  1.0
  O  O43  1  0.930  0.091  0.915  1.0
[/CIF]
.
The material structure described by Y2Hf2O7 crystallizes in the tetragonal P4_12_12 space group. Y(1) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. Hf(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing HfO5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and two equivalent Hf(1) atoms to form distorted OY2Hf2 trigonal pyramids that share corners with two equivalent O(2)Y3Hf tetrahedra, corners with two equivalent O(1)Y2Hf2 trigonal pyramids, edges with three equivalent O(2)Y3Hf tetrahedra, and  an edgeedge with one O(1)Y2Hf2 trigonal pyramid. In the second O site, O(2) is bonded to three equivalent Y(1) and one Hf(1) atom to form distorted OY3Hf tetrahedra that share corners with four equivalent O(2)Y3Hf tetrahedra, corners with two equivalent O(1)Y2Hf2 trigonal pyramids,  an edgeedge with one O(2)Y3Hf tetrahedra, and edges with three equivalent O(1)Y2Hf2 trigonal pyramids. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Y(1) and one Hf(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Hf(1) atoms. is represented by the CIF file [CIF]
data_Y2Hf2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.314
_cell_length_b   7.314
_cell_length_c   12.524
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   669.977
_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
  Y  Y0  1  0.137  0.625  0.134  1.0
  Y  Y1  1  0.125  0.363  0.884  1.0
  Y  Y2  1  0.375  0.863  0.366  1.0
  Y  Y3  1  0.363  0.125  0.116  1.0
  Y  Y4  1  0.637  0.875  0.616  1.0
  Y  Y5  1  0.625  0.137  0.866  1.0
  Y  Y6  1  0.875  0.637  0.384  1.0
  Y  Y7  1  0.863  0.375  0.634  1.0
  Hf  Hf8  1  0.099  0.872  0.595  1.0
  Hf  Hf9  1  0.128  0.901  0.905  1.0
  Hf  Hf10  1  0.372  0.401  0.345  1.0
  Hf  Hf11  1  0.401  0.372  0.655  1.0
  Hf  Hf12  1  0.599  0.628  0.155  1.0
  Hf  Hf13  1  0.628  0.599  0.845  1.0
  Hf  Hf14  1  0.872  0.099  0.405  1.0
  Hf  Hf15  1  0.901  0.128  0.095  1.0
  O  O16  1  0.070  0.909  0.415  1.0
  O  O17  1  0.082  0.326  0.074  1.0
  O  O18  1  0.091  0.930  0.085  1.0
  O  O19  1  0.153  0.640  0.953  1.0
  O  O20  1  0.174  0.582  0.324  1.0
  O  O21  1  0.140  0.347  0.703  1.0
  O  O22  1  0.143  0.857  0.750  1.0
  O  O23  1  0.357  0.357  0.500  1.0
  O  O24  1  0.360  0.847  0.547  1.0
  O  O25  1  0.326  0.082  0.926  1.0
  O  O26  1  0.347  0.140  0.297  1.0
  O  O27  1  0.409  0.430  0.165  1.0
  O  O28  1  0.418  0.826  0.176  1.0
  O  O29  1  0.430  0.409  0.835  1.0
  O  O30  1  0.570  0.591  0.335  1.0
  O  O31  1  0.582  0.174  0.676  1.0
  O  O32  1  0.591  0.570  0.665  1.0
  O  O33  1  0.653  0.860  0.797  1.0
  O  O34  1  0.674  0.918  0.426  1.0
  O  O35  1  0.640  0.153  0.047  1.0
  O  O36  1  0.643  0.643  0.000  1.0
  O  O37  1  0.857  0.143  0.250  1.0
  O  O38  1  0.860  0.653  0.203  1.0
  O  O39  1  0.826  0.418  0.824  1.0
  O  O40  1  0.847  0.360  0.453  1.0
  O  O41  1  0.909  0.070  0.585  1.0
  O  O42  1  0.918  0.674  0.574  1.0
  O  O43  1  0.930  0.091  0.915  1.0
[/CIF]
.