The crystal structure described by Sr2Ti2O5 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 10-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. In the second Sr site, Sr(2) is bonded in a 10-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form TiO6 octahedra that share corners with four equivalent Ti(1)O6 octahedra and  a cornercorner with one Ti(3)O4 trigonal pyramid. The corner-sharing octahedral tilt angles are 6°. In the second Ti site, Ti(2) is bonded in a rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(4) atoms. In the third Ti site, Ti(3) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form corner-sharing TiO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 15°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Ti(1) atoms to form a mixture of distorted corner, edge, and face-sharing OSr4Ti2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Ti(1), and one Ti(3) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to two equivalent Sr(1), two equivalent Sr(2), one Ti(2), and one Ti(3) atom. is represented by the CIF file [CIF]
data_Sr2Ti2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.805
_cell_length_b   8.805
_cell_length_c   8.805
_cell_angle_alpha   142.754
_cell_angle_beta   142.731
_cell_angle_gamma   53.712
_symmetry_Int_Tables_number   1
_cell_volume   248.600
_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
  Sr  Sr0  1  0.116  0.632  0.485  1.0
  Sr  Sr1  1  0.350  0.868  0.482  1.0
  Sr  Sr2  1  0.614  0.132  0.482  1.0
  Sr  Sr3  1  0.853  0.368  0.485  1.0
  Ti  Ti4  1  0.234  0.250  0.983  1.0
  Ti  Ti5  1  0.733  0.750  0.983  1.0
  Ti  Ti6  1  0.965  0.000  0.965  1.0
  Ti  Ti7  1  0.498  0.500  0.998  1.0
  O  O8  1  0.490  0.507  0.483  1.0
  O  O9  1  0.976  0.493  0.983  1.0
  O  O10  1  0.490  0.007  0.983  1.0
  O  O11  1  0.976  0.993  0.483  1.0
  O  O12  1  0.141  0.121  0.021  1.0
  O  O13  1  0.325  0.379  0.946  1.0
  O  O14  1  0.567  0.621  0.946  1.0
  O  O15  1  0.900  0.879  0.021  1.0
  O  O16  1  0.724  0.756  0.480  1.0
  O  O17  1  0.724  0.244  0.968  1.0
[/CIF]
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The crystal structure described by Sr2Ti2O5 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 10-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. In the second Sr site, Sr(2) is bonded in a 10-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form TiO6 octahedra that share corners with four equivalent Ti(1)O6 octahedra and  a cornercorner with one Ti(3)O4 trigonal pyramid. The corner-sharing octahedral tilt angles are 6°. In the second Ti site, Ti(2) is bonded in a rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(4) atoms. In the third Ti site, Ti(3) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form corner-sharing TiO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 15°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Ti(1) atoms to form a mixture of distorted corner, edge, and face-sharing OSr4Ti2 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Ti(1), and one Ti(3) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to two equivalent Sr(1), two equivalent Sr(2), one Ti(2), and one Ti(3) atom. is represented by the CIF file [CIF]
data_Sr2Ti2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.805
_cell_length_b   8.805
_cell_length_c   8.805
_cell_angle_alpha   142.754
_cell_angle_beta   142.731
_cell_angle_gamma   53.712
_symmetry_Int_Tables_number   1
_cell_volume   248.600
_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
  Sr  Sr0  1  0.116  0.632  0.485  1.0
  Sr  Sr1  1  0.350  0.868  0.482  1.0
  Sr  Sr2  1  0.614  0.132  0.482  1.0
  Sr  Sr3  1  0.853  0.368  0.485  1.0
  Ti  Ti4  1  0.234  0.250  0.983  1.0
  Ti  Ti5  1  0.733  0.750  0.983  1.0
  Ti  Ti6  1  0.965  0.000  0.965  1.0
  Ti  Ti7  1  0.498  0.500  0.998  1.0
  O  O8  1  0.490  0.507  0.483  1.0
  O  O9  1  0.976  0.493  0.983  1.0
  O  O10  1  0.490  0.007  0.983  1.0
  O  O11  1  0.976  0.993  0.483  1.0
  O  O12  1  0.141  0.121  0.021  1.0
  O  O13  1  0.325  0.379  0.946  1.0
  O  O14  1  0.567  0.621  0.946  1.0
  O  O15  1  0.900  0.879  0.021  1.0
  O  O16  1  0.724  0.756  0.480  1.0
  O  O17  1  0.724  0.244  0.968  1.0
[/CIF]
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