The material described by Er2TiO5 crystallizes in the orthorhombic Cmcm space group. Er(1) is bonded to one O(3), two equivalent O(1), and three equivalent O(2) atoms to form distorted ErO6 pentagonal pyramids that share  a cornercorner with one Ti(1)O6 octahedra, corners with three equivalent Er(1)O6 pentagonal pyramids, edges with three equivalent Ti(1)O6 octahedra, and edges with three equivalent Er(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 30°. Ti(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with two equivalent Er(1)O6 pentagonal pyramids, and edges with six equivalent Er(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 33°. 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 Er(1) and one Ti(1) atom. In the second O site, O(2) is bonded to three equivalent Er(1) and one Ti(1) atom to form OEr3Ti trigonal pyramids that share  a cornercorner with one O(3)Er2Ti2 tetrahedra, corners with three equivalent O(2)Er3Ti trigonal pyramids, edges with two equivalent O(3)Er2Ti2 tetrahedra, and edges with two equivalent O(2)Er3Ti trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Er(1) and two equivalent Ti(1) atoms to form distorted OEr2Ti2 tetrahedra that share corners with two equivalent O(3)Er2Ti2 tetrahedra, corners with two equivalent O(2)Er3Ti trigonal pyramids, and edges with four equivalent O(2)Er3Ti trigonal pyramids. is represented by the CIF file [CIF]
data_Er2TiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.842
_cell_length_b   5.842
_cell_length_c   10.451
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   139.208
_symmetry_Int_Tables_number   1
_cell_volume   233.032
_cell_formula_units_Z   2
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  0.143  0.857  0.931  1.0
  Er  Er1  1  0.143  0.857  0.569  1.0
  Er  Er2  1  0.857  0.143  0.069  1.0
  Er  Er3  1  0.857  0.143  0.431  1.0
  Ti  Ti4  1  0.173  0.827  0.250  1.0
  Ti  Ti5  1  0.827  0.173  0.750  1.0
  O  O6  1  0.052  0.948  0.377  1.0
  O  O7  1  0.052  0.948  0.123  1.0
  O  O8  1  0.708  0.292  0.910  1.0
  O  O9  1  0.708  0.292  0.590  1.0
  O  O10  1  0.272  0.728  0.750  1.0
  O  O11  1  0.728  0.272  0.250  1.0
  O  O12  1  0.292  0.708  0.090  1.0
  O  O13  1  0.292  0.708  0.410  1.0
  O  O14  1  0.948  0.052  0.623  1.0
  O  O15  1  0.948  0.052  0.877  1.0
[/CIF]
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The material described by Er2TiO5 crystallizes in the orthorhombic Cmcm space group. Er(1) is bonded to one O(3), two equivalent O(1), and three equivalent O(2) atoms to form distorted ErO6 pentagonal pyramids that share  a cornercorner with one Ti(1)O6 octahedra, corners with three equivalent Er(1)O6 pentagonal pyramids, edges with three equivalent Ti(1)O6 octahedra, and edges with three equivalent Er(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 30°. Ti(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with two equivalent Er(1)O6 pentagonal pyramids, and edges with six equivalent Er(1)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 33°. 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 Er(1) and one Ti(1) atom. In the second O site, O(2) is bonded to three equivalent Er(1) and one Ti(1) atom to form OEr3Ti trigonal pyramids that share  a cornercorner with one O(3)Er2Ti2 tetrahedra, corners with three equivalent O(2)Er3Ti trigonal pyramids, edges with two equivalent O(3)Er2Ti2 tetrahedra, and edges with two equivalent O(2)Er3Ti trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Er(1) and two equivalent Ti(1) atoms to form distorted OEr2Ti2 tetrahedra that share corners with two equivalent O(3)Er2Ti2 tetrahedra, corners with two equivalent O(2)Er3Ti trigonal pyramids, and edges with four equivalent O(2)Er3Ti trigonal pyramids. is represented by the CIF file [CIF]
data_Er2TiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.842
_cell_length_b   5.842
_cell_length_c   10.451
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   139.208
_symmetry_Int_Tables_number   1
_cell_volume   233.032
_cell_formula_units_Z   2
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  0.143  0.857  0.931  1.0
  Er  Er1  1  0.143  0.857  0.569  1.0
  Er  Er2  1  0.857  0.143  0.069  1.0
  Er  Er3  1  0.857  0.143  0.431  1.0
  Ti  Ti4  1  0.173  0.827  0.250  1.0
  Ti  Ti5  1  0.827  0.173  0.750  1.0
  O  O6  1  0.052  0.948  0.377  1.0
  O  O7  1  0.052  0.948  0.123  1.0
  O  O8  1  0.708  0.292  0.910  1.0
  O  O9  1  0.708  0.292  0.590  1.0
  O  O10  1  0.272  0.728  0.750  1.0
  O  O11  1  0.728  0.272  0.250  1.0
  O  O12  1  0.292  0.708  0.090  1.0
  O  O13  1  0.292  0.708  0.410  1.0
  O  O14  1  0.948  0.052  0.623  1.0
  O  O15  1  0.948  0.052  0.877  1.0
[/CIF]
.