The material structure described by Er2Bi2O7 crystallizes in the tetragonal P4_1 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), one O(3), one O(7), two equivalent O(2), and two equivalent O(4) atoms to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Bi(2)O5 trigonal bipyramid, corners with two equivalent Bi(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 pentagonal bipyramids, edges with three equivalent Er(2)O7 pentagonal bipyramids,  an edgeedge with one Bi(1)O5 trigonal bipyramid, and edges with two equivalent Bi(2)O5 trigonal bipyramids. In the second Er site, Er(2) is bonded to one O(1), one O(2), one O(3), two equivalent O(6), and two equivalent O(7) atoms to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Bi(1)O5 trigonal bipyramid, corners with two equivalent Bi(2)O5 trigonal bipyramids, edges with two equivalent Er(2)O7 pentagonal bipyramids, edges with three equivalent Er(1)O7 pentagonal bipyramids,  an edgeedge with one Bi(2)O5 trigonal bipyramid, and edges with two equivalent Bi(1)O5 trigonal bipyramids. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form distorted BiO5 trigonal bipyramids that share  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with two equivalent Er(1)O7 pentagonal bipyramids,  a cornercorner with one Bi(2)O5 trigonal bipyramid,  an edgeedge with one Er(1)O7 pentagonal bipyramid, edges with two equivalent Er(2)O7 pentagonal bipyramids, and  an edgeedge with one Bi(2)O5 trigonal bipyramid. In the second Bi site, Bi(2) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted BiO5 trigonal bipyramids that share  a cornercorner with one Er(1)O7 pentagonal bipyramid, corners with two equivalent Er(2)O7 pentagonal bipyramids,  a cornercorner with one Bi(1)O5 trigonal bipyramid,  an edgeedge with one Er(2)O7 pentagonal bipyramid, edges with two equivalent Er(1)O7 pentagonal bipyramids, and  an edgeedge with one Bi(1)O5 trigonal bipyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Er(1), one Er(2), one Bi(1), and one Bi(2) atom to form distorted OEr2Bi2 trigonal pyramids that share corners with two equivalent O(3)Er2Bi2 tetrahedra, corners with two equivalent O(7)Er3Bi tetrahedra,  an edgeedge with one O(3)Er2Bi2 tetrahedra,  an edgeedge with one O(7)Er3Bi tetrahedra, and edges with two equivalent O(2)Er3Bi tetrahedra. In the second O site, O(2) is bonded to one Er(2), two equivalent Er(1), and one Bi(1) atom to form OEr3Bi tetrahedra that share corners with two equivalent O(3)Er2Bi2 tetrahedra, corners with two equivalent O(2)Er3Bi tetrahedra, corners with two equivalent O(7)Er3Bi tetrahedra,  an edgeedge with one O(3)Er2Bi2 tetrahedra,  an edgeedge with one O(7)Er3Bi tetrahedra, and edges with two equivalent O(1)Er2Bi2 trigonal pyramids. In the third O site, O(3) is bonded to one Er(1), one Er(2), one Bi(1), and one Bi(2) atom to form OEr2Bi2 tetrahedra that share corners with two equivalent O(2)Er3Bi tetrahedra, corners with two equivalent O(1)Er2Bi2 trigonal pyramids,  an edgeedge with one O(2)Er3Bi tetrahedra, edges with two equivalent O(7)Er3Bi tetrahedra, and  an edgeedge with one O(1)Er2Bi2 trigonal pyramid. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Bi(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Bi(1) and one Bi(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Er(2) and one Bi(1) atom. In the seventh O site, O(7) is bonded to one Er(1), two equivalent Er(2), and one Bi(2) atom to form distorted OEr3Bi tetrahedra that share corners with two equivalent O(2)Er3Bi tetrahedra, corners with two equivalent O(7)Er3Bi tetrahedra, corners with two equivalent O(1)Er2Bi2 trigonal pyramids,  an edgeedge with one O(2)Er3Bi tetrahedra, edges with two equivalent O(3)Er2Bi2 tetrahedra, and  an edgeedge with one O(1)Er2Bi2 trigonal pyramid. is represented by the CIF file [CIF]
data_Er2Bi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.330
_cell_length_b   7.330
_cell_length_c   13.119
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   704.788
_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  0.151  0.120  0.640  1.0
  Er  Er1  1  0.120  0.849  0.390  1.0
  Er  Er2  1  0.377  0.351  0.860  1.0
  Er  Er3  1  0.351  0.623  0.610  1.0
  Er  Er4  1  0.649  0.377  0.110  1.0
  Er  Er5  1  0.623  0.649  0.360  1.0
  Er  Er6  1  0.880  0.151  0.890  1.0
  Er  Er7  1  0.849  0.880  0.140  1.0
  Bi  Bi8  1  0.123  0.381  0.098  1.0
  Bi  Bi9  1  0.124  0.380  0.409  1.0
  Bi  Bi10  1  0.381  0.877  0.848  1.0
  Bi  Bi11  1  0.380  0.876  0.159  1.0
  Bi  Bi12  1  0.620  0.124  0.659  1.0
  Bi  Bi13  1  0.619  0.123  0.348  1.0
  Bi  Bi14  1  0.876  0.620  0.909  1.0
  Bi  Bi15  1  0.877  0.619  0.598  1.0
  O  O16  1  0.075  0.405  0.914  1.0
  O  O17  1  0.092  0.820  0.574  1.0
  O  O18  1  0.108  0.416  0.579  1.0
  O  O19  1  0.168  0.113  0.467  1.0
  O  O20  1  0.180  0.092  0.824  1.0
  O  O21  1  0.113  0.832  0.217  1.0
  O  O22  1  0.179  0.315  0.258  1.0
  O  O23  1  0.315  0.821  0.008  1.0
  O  O24  1  0.391  0.324  0.029  1.0
  O  O25  1  0.318  0.589  0.424  1.0
  O  O26  1  0.324  0.609  0.779  1.0
  O  O27  1  0.405  0.925  0.664  1.0
  O  O28  1  0.411  0.318  0.674  1.0
  O  O29  1  0.416  0.892  0.329  1.0
  O  O30  1  0.584  0.108  0.829  1.0
  O  O31  1  0.589  0.682  0.174  1.0
  O  O32  1  0.595  0.075  0.164  1.0
  O  O33  1  0.676  0.391  0.279  1.0
  O  O34  1  0.682  0.411  0.924  1.0
  O  O35  1  0.609  0.676  0.529  1.0
  O  O36  1  0.685  0.179  0.508  1.0
  O  O37  1  0.821  0.685  0.758  1.0
  O  O38  1  0.887  0.168  0.717  1.0
  O  O39  1  0.820  0.908  0.324  1.0
  O  O40  1  0.832  0.887  0.967  1.0
  O  O41  1  0.892  0.584  0.079  1.0
  O  O42  1  0.908  0.180  0.074  1.0
  O  O43  1  0.925  0.595  0.414  1.0
[/CIF]
.
The material structure described by Er2Bi2O7 crystallizes in the tetragonal P4_1 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), one O(3), one O(7), two equivalent O(2), and two equivalent O(4) atoms to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Bi(2)O5 trigonal bipyramid, corners with two equivalent Bi(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 pentagonal bipyramids, edges with three equivalent Er(2)O7 pentagonal bipyramids,  an edgeedge with one Bi(1)O5 trigonal bipyramid, and edges with two equivalent Bi(2)O5 trigonal bipyramids. In the second Er site, Er(2) is bonded to one O(1), one O(2), one O(3), two equivalent O(6), and two equivalent O(7) atoms to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Bi(1)O5 trigonal bipyramid, corners with two equivalent Bi(2)O5 trigonal bipyramids, edges with two equivalent Er(2)O7 pentagonal bipyramids, edges with three equivalent Er(1)O7 pentagonal bipyramids,  an edgeedge with one Bi(2)O5 trigonal bipyramid, and edges with two equivalent Bi(1)O5 trigonal bipyramids. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form distorted BiO5 trigonal bipyramids that share  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with two equivalent Er(1)O7 pentagonal bipyramids,  a cornercorner with one Bi(2)O5 trigonal bipyramid,  an edgeedge with one Er(1)O7 pentagonal bipyramid, edges with two equivalent Er(2)O7 pentagonal bipyramids, and  an edgeedge with one Bi(2)O5 trigonal bipyramid. In the second Bi site, Bi(2) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted BiO5 trigonal bipyramids that share  a cornercorner with one Er(1)O7 pentagonal bipyramid, corners with two equivalent Er(2)O7 pentagonal bipyramids,  a cornercorner with one Bi(1)O5 trigonal bipyramid,  an edgeedge with one Er(2)O7 pentagonal bipyramid, edges with two equivalent Er(1)O7 pentagonal bipyramids, and  an edgeedge with one Bi(1)O5 trigonal bipyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Er(1), one Er(2), one Bi(1), and one Bi(2) atom to form distorted OEr2Bi2 trigonal pyramids that share corners with two equivalent O(3)Er2Bi2 tetrahedra, corners with two equivalent O(7)Er3Bi tetrahedra,  an edgeedge with one O(3)Er2Bi2 tetrahedra,  an edgeedge with one O(7)Er3Bi tetrahedra, and edges with two equivalent O(2)Er3Bi tetrahedra. In the second O site, O(2) is bonded to one Er(2), two equivalent Er(1), and one Bi(1) atom to form OEr3Bi tetrahedra that share corners with two equivalent O(3)Er2Bi2 tetrahedra, corners with two equivalent O(2)Er3Bi tetrahedra, corners with two equivalent O(7)Er3Bi tetrahedra,  an edgeedge with one O(3)Er2Bi2 tetrahedra,  an edgeedge with one O(7)Er3Bi tetrahedra, and edges with two equivalent O(1)Er2Bi2 trigonal pyramids. In the third O site, O(3) is bonded to one Er(1), one Er(2), one Bi(1), and one Bi(2) atom to form OEr2Bi2 tetrahedra that share corners with two equivalent O(2)Er3Bi tetrahedra, corners with two equivalent O(1)Er2Bi2 trigonal pyramids,  an edgeedge with one O(2)Er3Bi tetrahedra, edges with two equivalent O(7)Er3Bi tetrahedra, and  an edgeedge with one O(1)Er2Bi2 trigonal pyramid. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Bi(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Bi(1) and one Bi(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Er(2) and one Bi(1) atom. In the seventh O site, O(7) is bonded to one Er(1), two equivalent Er(2), and one Bi(2) atom to form distorted OEr3Bi tetrahedra that share corners with two equivalent O(2)Er3Bi tetrahedra, corners with two equivalent O(7)Er3Bi tetrahedra, corners with two equivalent O(1)Er2Bi2 trigonal pyramids,  an edgeedge with one O(2)Er3Bi tetrahedra, edges with two equivalent O(3)Er2Bi2 tetrahedra, and  an edgeedge with one O(1)Er2Bi2 trigonal pyramid. is represented by the CIF file [CIF]
data_Er2Bi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.330
_cell_length_b   7.330
_cell_length_c   13.119
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   704.788
_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  0.151  0.120  0.640  1.0
  Er  Er1  1  0.120  0.849  0.390  1.0
  Er  Er2  1  0.377  0.351  0.860  1.0
  Er  Er3  1  0.351  0.623  0.610  1.0
  Er  Er4  1  0.649  0.377  0.110  1.0
  Er  Er5  1  0.623  0.649  0.360  1.0
  Er  Er6  1  0.880  0.151  0.890  1.0
  Er  Er7  1  0.849  0.880  0.140  1.0
  Bi  Bi8  1  0.123  0.381  0.098  1.0
  Bi  Bi9  1  0.124  0.380  0.409  1.0
  Bi  Bi10  1  0.381  0.877  0.848  1.0
  Bi  Bi11  1  0.380  0.876  0.159  1.0
  Bi  Bi12  1  0.620  0.124  0.659  1.0
  Bi  Bi13  1  0.619  0.123  0.348  1.0
  Bi  Bi14  1  0.876  0.620  0.909  1.0
  Bi  Bi15  1  0.877  0.619  0.598  1.0
  O  O16  1  0.075  0.405  0.914  1.0
  O  O17  1  0.092  0.820  0.574  1.0
  O  O18  1  0.108  0.416  0.579  1.0
  O  O19  1  0.168  0.113  0.467  1.0
  O  O20  1  0.180  0.092  0.824  1.0
  O  O21  1  0.113  0.832  0.217  1.0
  O  O22  1  0.179  0.315  0.258  1.0
  O  O23  1  0.315  0.821  0.008  1.0
  O  O24  1  0.391  0.324  0.029  1.0
  O  O25  1  0.318  0.589  0.424  1.0
  O  O26  1  0.324  0.609  0.779  1.0
  O  O27  1  0.405  0.925  0.664  1.0
  O  O28  1  0.411  0.318  0.674  1.0
  O  O29  1  0.416  0.892  0.329  1.0
  O  O30  1  0.584  0.108  0.829  1.0
  O  O31  1  0.589  0.682  0.174  1.0
  O  O32  1  0.595  0.075  0.164  1.0
  O  O33  1  0.676  0.391  0.279  1.0
  O  O34  1  0.682  0.411  0.924  1.0
  O  O35  1  0.609  0.676  0.529  1.0
  O  O36  1  0.685  0.179  0.508  1.0
  O  O37  1  0.821  0.685  0.758  1.0
  O  O38  1  0.887  0.168  0.717  1.0
  O  O39  1  0.820  0.908  0.324  1.0
  O  O40  1  0.832  0.887  0.967  1.0
  O  O41  1  0.892  0.584  0.079  1.0
  O  O42  1  0.908  0.180  0.074  1.0
  O  O43  1  0.925  0.595  0.414  1.0
[/CIF]
.