The crystal structure described by Er2Ge2O7 crystallizes in the tetragonal P4_12_12 space group. Er(1) is bonded to two equivalent O(1), two equivalent O(4), and three equivalent O(2) atoms to form distorted ErO7 pentagonal bipyramids that share corners with five equivalent Ge(1)O4 tetrahedra, edges with five equivalent Er(1)O7 pentagonal bipyramids, and  an edgeedge with one Ge(1)O4 tetrahedra. Ge(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form GeO4 tetrahedra that share corners with five equivalent Er(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(1)O4 tetrahedra, and  an edgeedge with one Er(1)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ge(1) atoms. In the second O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Er(1) and one Ge(1) atom. In the third O site, O(1) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Ge(1) atom. In the fourth O site, O(2) is bonded to three equivalent Er(1) and one Ge(1) atom to form a mixture of distorted edge and corner-sharing OEr3Ge trigonal pyramids. is represented by the CIF card [CIF]
data_Er2Ge2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.758
_cell_length_b   6.758
_cell_length_c   12.304
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   561.978
_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
  Er  Er0  1  0.645  0.126  0.365  1.0
  Er  Er1  1  0.355  0.874  0.865  1.0
  Er  Er2  1  0.126  0.645  0.635  1.0
  Er  Er3  1  0.626  0.855  0.115  1.0
  Er  Er4  1  0.374  0.145  0.615  1.0
  Er  Er5  1  0.855  0.626  0.885  1.0
  Er  Er6  1  0.145  0.374  0.385  1.0
  Er  Er7  1  0.874  0.355  0.135  1.0
  Ge  Ge8  1  0.849  0.100  0.882  1.0
  Ge  Ge9  1  0.151  0.900  0.382  1.0
  Ge  Ge10  1  0.100  0.849  0.118  1.0
  Ge  Ge11  1  0.600  0.651  0.632  1.0
  Ge  Ge12  1  0.400  0.349  0.132  1.0
  Ge  Ge13  1  0.651  0.600  0.368  1.0
  Ge  Ge14  1  0.349  0.400  0.868  1.0
  Ge  Ge15  1  0.900  0.151  0.618  1.0
  O  O16  1  0.857  0.320  0.956  1.0
  O  O17  1  0.143  0.680  0.456  1.0
  O  O18  1  0.320  0.857  0.044  1.0
  O  O19  1  0.820  0.643  0.706  1.0
  O  O20  1  0.180  0.357  0.206  1.0
  O  O21  1  0.643  0.820  0.294  1.0
  O  O22  1  0.357  0.180  0.794  1.0
  O  O23  1  0.680  0.143  0.544  1.0
  O  O24  1  0.662  0.936  0.929  1.0
  O  O25  1  0.338  0.064  0.429  1.0
  O  O26  1  0.936  0.662  0.071  1.0
  O  O27  1  0.436  0.838  0.679  1.0
  O  O28  1  0.564  0.162  0.179  1.0
  O  O29  1  0.838  0.436  0.321  1.0
  O  O30  1  0.162  0.564  0.821  1.0
  O  O31  1  0.064  0.338  0.571  1.0
  O  O32  1  0.804  0.196  0.750  1.0
  O  O33  1  0.304  0.304  0.000  1.0
  O  O34  1  0.696  0.696  0.500  1.0
  O  O35  1  0.196  0.804  0.250  1.0
  O  O36  1  0.078  0.966  0.622  1.0
  O  O37  1  0.534  0.578  0.872  1.0
  O  O38  1  0.466  0.422  0.372  1.0
  O  O39  1  0.578  0.534  0.128  1.0
  O  O40  1  0.422  0.466  0.628  1.0
  O  O41  1  0.922  0.034  0.122  1.0
  O  O42  1  0.966  0.078  0.378  1.0
  O  O43  1  0.034  0.922  0.878  1.0
[/CIF]
.
The crystal structure described by Er2Ge2O7 crystallizes in the tetragonal P4_12_12 space group. Er(1) is bonded to two equivalent O(1), two equivalent O(4), and three equivalent O(2) atoms to form distorted ErO7 pentagonal bipyramids that share corners with five equivalent Ge(1)O4 tetrahedra, edges with five equivalent Er(1)O7 pentagonal bipyramids, and  an edgeedge with one Ge(1)O4 tetrahedra. Ge(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form GeO4 tetrahedra that share corners with five equivalent Er(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(1)O4 tetrahedra, and  an edgeedge with one Er(1)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ge(1) atoms. In the second O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Er(1) and one Ge(1) atom. In the third O site, O(1) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Ge(1) atom. In the fourth O site, O(2) is bonded to three equivalent Er(1) and one Ge(1) atom to form a mixture of distorted edge and corner-sharing OEr3Ge trigonal pyramids. is represented by the CIF card [CIF]
data_Er2Ge2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.758
_cell_length_b   6.758
_cell_length_c   12.304
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   561.978
_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
  Er  Er0  1  0.645  0.126  0.365  1.0
  Er  Er1  1  0.355  0.874  0.865  1.0
  Er  Er2  1  0.126  0.645  0.635  1.0
  Er  Er3  1  0.626  0.855  0.115  1.0
  Er  Er4  1  0.374  0.145  0.615  1.0
  Er  Er5  1  0.855  0.626  0.885  1.0
  Er  Er6  1  0.145  0.374  0.385  1.0
  Er  Er7  1  0.874  0.355  0.135  1.0
  Ge  Ge8  1  0.849  0.100  0.882  1.0
  Ge  Ge9  1  0.151  0.900  0.382  1.0
  Ge  Ge10  1  0.100  0.849  0.118  1.0
  Ge  Ge11  1  0.600  0.651  0.632  1.0
  Ge  Ge12  1  0.400  0.349  0.132  1.0
  Ge  Ge13  1  0.651  0.600  0.368  1.0
  Ge  Ge14  1  0.349  0.400  0.868  1.0
  Ge  Ge15  1  0.900  0.151  0.618  1.0
  O  O16  1  0.857  0.320  0.956  1.0
  O  O17  1  0.143  0.680  0.456  1.0
  O  O18  1  0.320  0.857  0.044  1.0
  O  O19  1  0.820  0.643  0.706  1.0
  O  O20  1  0.180  0.357  0.206  1.0
  O  O21  1  0.643  0.820  0.294  1.0
  O  O22  1  0.357  0.180  0.794  1.0
  O  O23  1  0.680  0.143  0.544  1.0
  O  O24  1  0.662  0.936  0.929  1.0
  O  O25  1  0.338  0.064  0.429  1.0
  O  O26  1  0.936  0.662  0.071  1.0
  O  O27  1  0.436  0.838  0.679  1.0
  O  O28  1  0.564  0.162  0.179  1.0
  O  O29  1  0.838  0.436  0.321  1.0
  O  O30  1  0.162  0.564  0.821  1.0
  O  O31  1  0.064  0.338  0.571  1.0
  O  O32  1  0.804  0.196  0.750  1.0
  O  O33  1  0.304  0.304  0.000  1.0
  O  O34  1  0.696  0.696  0.500  1.0
  O  O35  1  0.196  0.804  0.250  1.0
  O  O36  1  0.078  0.966  0.622  1.0
  O  O37  1  0.534  0.578  0.872  1.0
  O  O38  1  0.466  0.422  0.372  1.0
  O  O39  1  0.578  0.534  0.128  1.0
  O  O40  1  0.422  0.466  0.628  1.0
  O  O41  1  0.922  0.034  0.122  1.0
  O  O42  1  0.966  0.078  0.378  1.0
  O  O43  1  0.034  0.922  0.878  1.0
[/CIF]
.