The material structure described by Er2TiO5 crystallizes in the orthorhombic Pnma 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(5), two equivalent O(2), and two equivalent O(4) atoms to form distorted ErO7 hexagonal pyramids that share corners with two equivalent Er(2)O7 hexagonal pyramids, corners with three equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 hexagonal pyramids, edges with three equivalent Er(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. In the second Er site, Er(2) is bonded to one O(4), one O(5), two equivalent O(3), and three equivalent O(1) atoms to form distorted ErO7 hexagonal pyramids that share corners with two equivalent Er(1)O7 hexagonal pyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with three equivalent Er(1)O7 hexagonal pyramids, edges with four equivalent Er(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. Ti(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form distorted TiO5 trigonal bipyramids that share  a cornercorner with one Er(2)O7 hexagonal pyramid, corners with three equivalent Er(1)O7 hexagonal pyramids, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 hexagonal pyramids, and edges with two equivalent Er(2)O7 hexagonal pyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Er(1) and three equivalent Er(2) atoms to form OEr4 tetrahedra that share corners with two equivalent O(5)Er2Ti2 tetrahedra, corners with two equivalent O(1)Er4 tetrahedra, corners with five equivalent O(3)Er3Ti tetrahedra, corners with five equivalent O(4)Er3Ti tetrahedra,  an edgeedge with one O(5)Er2Ti2 tetrahedra,  an edgeedge with one O(3)Er3Ti tetrahedra, and edges with two equivalent O(1)Er4 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one Ti(1) atom. In the third O site, O(3) is bonded to one Er(1), two equivalent Er(2), and one Ti(1) atom to form OEr3Ti tetrahedra that share  a cornercorner with one O(5)Er2Ti2 tetrahedra,  a cornercorner with one O(4)Er3Ti tetrahedra, corners with two equivalent O(3)Er3Ti tetrahedra, corners with five equivalent O(1)Er4 tetrahedra,  an edgeedge with one O(1)Er4 tetrahedra, edges with two equivalent O(5)Er2Ti2 tetrahedra, and edges with two equivalent O(4)Er3Ti tetrahedra. In the fourth O site, O(4) is bonded to one Er(2), two equivalent Er(1), and one Ti(1) atom to form OEr3Ti tetrahedra that share  a cornercorner with one O(5)Er2Ti2 tetrahedra,  a cornercorner with one O(3)Er3Ti tetrahedra, corners with two equivalent O(4)Er3Ti tetrahedra, corners with five equivalent O(1)Er4 tetrahedra, edges with two equivalent O(5)Er2Ti2 tetrahedra, and edges with two equivalent O(3)Er3Ti tetrahedra. In the fifth O site, O(5) is bonded to one Er(1), one Er(2), and two equivalent Ti(1) atoms to form distorted OEr2Ti2 tetrahedra that share  a cornercorner with one O(3)Er3Ti tetrahedra,  a cornercorner with one O(4)Er3Ti tetrahedra, corners with two equivalent O(5)Er2Ti2 tetrahedra, corners with two equivalent O(1)Er4 tetrahedra,  an edgeedge with one O(1)Er4 tetrahedra, edges with two equivalent O(3)Er3Ti tetrahedra, and edges with two equivalent O(4)Er3Ti tetrahedra. is represented by the CIF file [CIF]
data_Er2TiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.640
_cell_length_b   10.240
_cell_length_c   11.172
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   416.445
_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  0.250  0.118  0.275  1.0
  Er  Er1  1  0.250  0.136  0.943  1.0
  Er  Er2  1  0.750  0.364  0.443  1.0
  Er  Er3  1  0.750  0.382  0.775  1.0
  Er  Er4  1  0.250  0.618  0.225  1.0
  Er  Er5  1  0.250  0.636  0.557  1.0
  Er  Er6  1  0.750  0.864  0.057  1.0
  Er  Er7  1  0.750  0.882  0.725  1.0
  Ti  Ti8  1  0.250  0.171  0.618  1.0
  Ti  Ti9  1  0.750  0.329  0.118  1.0
  Ti  Ti10  1  0.250  0.671  0.882  1.0
  Ti  Ti11  1  0.750  0.829  0.382  1.0
  O  O12  1  0.750  0.006  0.895  1.0
  O  O13  1  0.250  0.002  0.654  1.0
  O  O14  1  0.250  0.224  0.455  1.0
  O  O15  1  0.750  0.247  0.271  1.0
  O  O16  1  0.750  0.237  0.615  1.0
  O  O17  1  0.250  0.263  0.115  1.0
  O  O18  1  0.250  0.253  0.771  1.0
  O  O19  1  0.750  0.276  0.955  1.0
  O  O20  1  0.750  0.498  0.154  1.0
  O  O21  1  0.250  0.494  0.395  1.0
  O  O22  1  0.750  0.506  0.605  1.0
  O  O23  1  0.250  0.502  0.846  1.0
  O  O24  1  0.250  0.724  0.045  1.0
  O  O25  1  0.750  0.747  0.229  1.0
  O  O26  1  0.750  0.737  0.885  1.0
  O  O27  1  0.250  0.763  0.385  1.0
  O  O28  1  0.250  0.753  0.729  1.0
  O  O29  1  0.750  0.776  0.545  1.0
  O  O30  1  0.750  0.998  0.346  1.0
  O  O31  1  0.250  0.994  0.105  1.0
[/CIF]
.
The material structure described by Er2TiO5 crystallizes in the orthorhombic Pnma 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(5), two equivalent O(2), and two equivalent O(4) atoms to form distorted ErO7 hexagonal pyramids that share corners with two equivalent Er(2)O7 hexagonal pyramids, corners with three equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 hexagonal pyramids, edges with three equivalent Er(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. In the second Er site, Er(2) is bonded to one O(4), one O(5), two equivalent O(3), and three equivalent O(1) atoms to form distorted ErO7 hexagonal pyramids that share corners with two equivalent Er(1)O7 hexagonal pyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with three equivalent Er(1)O7 hexagonal pyramids, edges with four equivalent Er(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. Ti(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form distorted TiO5 trigonal bipyramids that share  a cornercorner with one Er(2)O7 hexagonal pyramid, corners with three equivalent Er(1)O7 hexagonal pyramids, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 hexagonal pyramids, and edges with two equivalent Er(2)O7 hexagonal pyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Er(1) and three equivalent Er(2) atoms to form OEr4 tetrahedra that share corners with two equivalent O(5)Er2Ti2 tetrahedra, corners with two equivalent O(1)Er4 tetrahedra, corners with five equivalent O(3)Er3Ti tetrahedra, corners with five equivalent O(4)Er3Ti tetrahedra,  an edgeedge with one O(5)Er2Ti2 tetrahedra,  an edgeedge with one O(3)Er3Ti tetrahedra, and edges with two equivalent O(1)Er4 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one Ti(1) atom. In the third O site, O(3) is bonded to one Er(1), two equivalent Er(2), and one Ti(1) atom to form OEr3Ti tetrahedra that share  a cornercorner with one O(5)Er2Ti2 tetrahedra,  a cornercorner with one O(4)Er3Ti tetrahedra, corners with two equivalent O(3)Er3Ti tetrahedra, corners with five equivalent O(1)Er4 tetrahedra,  an edgeedge with one O(1)Er4 tetrahedra, edges with two equivalent O(5)Er2Ti2 tetrahedra, and edges with two equivalent O(4)Er3Ti tetrahedra. In the fourth O site, O(4) is bonded to one Er(2), two equivalent Er(1), and one Ti(1) atom to form OEr3Ti tetrahedra that share  a cornercorner with one O(5)Er2Ti2 tetrahedra,  a cornercorner with one O(3)Er3Ti tetrahedra, corners with two equivalent O(4)Er3Ti tetrahedra, corners with five equivalent O(1)Er4 tetrahedra, edges with two equivalent O(5)Er2Ti2 tetrahedra, and edges with two equivalent O(3)Er3Ti tetrahedra. In the fifth O site, O(5) is bonded to one Er(1), one Er(2), and two equivalent Ti(1) atoms to form distorted OEr2Ti2 tetrahedra that share  a cornercorner with one O(3)Er3Ti tetrahedra,  a cornercorner with one O(4)Er3Ti tetrahedra, corners with two equivalent O(5)Er2Ti2 tetrahedra, corners with two equivalent O(1)Er4 tetrahedra,  an edgeedge with one O(1)Er4 tetrahedra, edges with two equivalent O(3)Er3Ti tetrahedra, and edges with two equivalent O(4)Er3Ti tetrahedra. is represented by the CIF file [CIF]
data_Er2TiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.640
_cell_length_b   10.240
_cell_length_c   11.172
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   416.445
_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  0.250  0.118  0.275  1.0
  Er  Er1  1  0.250  0.136  0.943  1.0
  Er  Er2  1  0.750  0.364  0.443  1.0
  Er  Er3  1  0.750  0.382  0.775  1.0
  Er  Er4  1  0.250  0.618  0.225  1.0
  Er  Er5  1  0.250  0.636  0.557  1.0
  Er  Er6  1  0.750  0.864  0.057  1.0
  Er  Er7  1  0.750  0.882  0.725  1.0
  Ti  Ti8  1  0.250  0.171  0.618  1.0
  Ti  Ti9  1  0.750  0.329  0.118  1.0
  Ti  Ti10  1  0.250  0.671  0.882  1.0
  Ti  Ti11  1  0.750  0.829  0.382  1.0
  O  O12  1  0.750  0.006  0.895  1.0
  O  O13  1  0.250  0.002  0.654  1.0
  O  O14  1  0.250  0.224  0.455  1.0
  O  O15  1  0.750  0.247  0.271  1.0
  O  O16  1  0.750  0.237  0.615  1.0
  O  O17  1  0.250  0.263  0.115  1.0
  O  O18  1  0.250  0.253  0.771  1.0
  O  O19  1  0.750  0.276  0.955  1.0
  O  O20  1  0.750  0.498  0.154  1.0
  O  O21  1  0.250  0.494  0.395  1.0
  O  O22  1  0.750  0.506  0.605  1.0
  O  O23  1  0.250  0.502  0.846  1.0
  O  O24  1  0.250  0.724  0.045  1.0
  O  O25  1  0.750  0.747  0.229  1.0
  O  O26  1  0.750  0.737  0.885  1.0
  O  O27  1  0.250  0.763  0.385  1.0
  O  O28  1  0.250  0.753  0.729  1.0
  O  O29  1  0.750  0.776  0.545  1.0
  O  O30  1  0.750  0.998  0.346  1.0
  O  O31  1  0.250  0.994  0.105  1.0
[/CIF]
.