The compound described by Nd2Ti2O7 crystallizes in the monoclinic P2_1 space group. There are four inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 9-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(9), two equivalent O(1), and two equivalent O(2) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the third Nd site, Nd(3) is bonded in a 7-coordinate geometry to one O(11), one O(14), one O(9), two equivalent O(12), and two equivalent O(13) atoms. In the fourth Nd site, Nd(4) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(7), one O(8), and two equivalent O(14) atoms. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(3), one O(4), one O(5), one O(7), and two equivalent O(2) atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 19-44°. In the second Ti site, Ti(2) is bonded to one O(3), one O(4), one O(6), one O(8), and two equivalent O(1) atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 19-39°. In the third Ti site, Ti(3) is bonded to one O(10), one O(11), one O(14), one O(5), one O(7), and one O(9) atom to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 24-44°. In the fourth Ti site, Ti(4) is bonded to one O(10), one O(12), one O(13), one O(6), one O(8), and one O(9) atom to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 24-39°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Nd(2), two equivalent Nd(1), and two equivalent Ti(2) atoms. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Nd(2), two equivalent Nd(1), and two equivalent Ti(1) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nd(1), one Ti(1), and one Ti(2) atom. In the fourth O site, O(4) is bonded to one Nd(1), one Nd(2), one Ti(1), and one Ti(2) atom to form a mixture of distorted corner and edge-sharing ONd2Ti2 tetrahedra. In the fifth O site, O(5) is bonded to one Nd(1), one Nd(2), one Ti(1), and one Ti(3) atom to form distorted ONd2Ti2 tetrahedra that share  a cornercorner with one O(4)Nd2Ti2 tetrahedra,  a cornercorner with one O(14)Nd3Ti tetrahedra, corners with two equivalent O(6)Nd2Ti2 tetrahedra, and  an edgeedge with one O(4)Nd2Ti2 tetrahedra. In the sixth O site, O(6) is bonded to one Nd(1), one Nd(2), one Ti(2), and one Ti(4) atom to form distorted ONd2Ti2 tetrahedra that share  a cornercorner with one O(4)Nd2Ti2 tetrahedra,  a cornercorner with one O(12)Nd3Ti tetrahedra,  a cornercorner with one O(13)Nd3Ti tetrahedra, corners with two equivalent O(5)Nd2Ti2 tetrahedra, and  an edgeedge with one O(4)Nd2Ti2 tetrahedra. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Nd(2), one Nd(4), one Ti(1), and one Ti(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Nd(2), one Nd(4), one Ti(2), and one Ti(4) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Nd(1), one Nd(3), one Ti(3), and one Ti(4) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Nd(2), one Nd(4), one Ti(3), and one Ti(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nd(3), one Nd(4), and one Ti(3) atom. In the twelfth O site, O(12) is bonded to one Nd(4), two equivalent Nd(3), and one Ti(4) atom to form distorted ONd3Ti tetrahedra that share  a cornercorner with one O(6)Nd2Ti2 tetrahedra, corners with two equivalent O(12)Nd3Ti tetrahedra, corners with four equivalent O(14)Nd3Ti tetrahedra, and edges with three equivalent O(13)Nd3Ti tetrahedra. In the thirteenth O site, O(13) is bonded to one Nd(4), two equivalent Nd(3), and one Ti(4) atom to form distorted ONd3Ti tetrahedra that share  a cornercorner with one O(6)Nd2Ti2 tetrahedra, corners with two equivalent O(13)Nd3Ti tetrahedra, corners with two equivalent O(14)Nd3Ti tetrahedra,  an edgeedge with one O(14)Nd3Ti tetrahedra, and edges with three equivalent O(12)Nd3Ti tetrahedra. In the fourteenth O site, O(14) is bonded to one Nd(3), two equivalent Nd(4), and one Ti(3) atom to form distorted ONd3Ti tetrahedra that share  a cornercorner with one O(5)Nd2Ti2 tetrahedra, corners with two equivalent O(13)Nd3Ti tetrahedra, corners with two equivalent O(14)Nd3Ti tetrahedra, corners with four equivalent O(12)Nd3Ti tetrahedra, and  an edgeedge with one O(13)Nd3Ti tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nd2Ti2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.484
_cell_length_b   7.679
_cell_length_c   13.101
_cell_angle_alpha   81.505
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   545.647
_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
  Nd  Nd0  1  0.754  0.729  0.090  1.0
  Nd  Nd1  1  0.254  0.271  0.910  1.0
  Nd  Nd2  1  0.742  0.219  0.121  1.0
  Nd  Nd3  1  0.242  0.781  0.879  1.0
  Nd  Nd4  1  0.349  0.645  0.428  1.0
  Nd  Nd5  1  0.849  0.355  0.572  1.0
  Nd  Nd6  1  0.281  0.149  0.383  1.0
  Nd  Nd7  1  0.781  0.851  0.617  1.0
  Ti  Ti8  1  0.255  0.972  0.121  1.0
  Ti  Ti9  1  0.755  0.028  0.879  1.0
  Ti  Ti10  1  0.257  0.469  0.119  1.0
  Ti  Ti11  1  0.757  0.531  0.881  1.0
  Ti  Ti12  1  0.788  0.914  0.325  1.0
  Ti  Ti13  1  0.288  0.086  0.675  1.0
  Ti  Ti14  1  0.781  0.426  0.320  1.0
  Ti  Ti15  1  0.281  0.574  0.680  1.0
  O  O16  1  0.018  0.543  0.981  1.0
  O  O17  1  0.518  0.457  0.019  1.0
  O  O18  1  0.018  0.967  0.979  1.0
  O  O19  1  0.518  0.033  0.021  1.0
  O  O20  1  0.310  0.723  0.109  1.0
  O  O21  1  0.810  0.277  0.891  1.0
  O  O22  1  0.167  0.227  0.092  1.0
  O  O23  1  0.667  0.773  0.908  1.0
  O  O24  1  0.936  0.933  0.181  1.0
  O  O25  1  0.436  0.067  0.819  1.0
  O  O26  1  0.941  0.478  0.183  1.0
  O  O27  1  0.441  0.522  0.817  1.0
  O  O28  1  0.450  0.003  0.230  1.0
  O  O29  1  0.950  0.997  0.770  1.0
  O  O30  1  0.454  0.384  0.227  1.0
  O  O31  1  0.954  0.616  0.773  1.0
  O  O32  1  0.689  0.674  0.305  1.0
  O  O33  1  0.189  0.326  0.695  1.0
  O  O34  1  0.847  0.173  0.306  1.0
  O  O35  1  0.347  0.827  0.694  1.0
  O  O36  1  0.073  0.874  0.388  1.0
  O  O37  1  0.064  0.630  0.571  1.0
  O  O38  1  0.573  0.126  0.612  1.0
  O  O39  1  0.549  0.579  0.594  1.0
  O  O40  1  0.581  0.909  0.442  1.0
  O  O41  1  0.081  0.091  0.558  1.0
  O  O42  1  0.564  0.370  0.429  1.0
  O  O43  1  0.049  0.421  0.406  1.0
[/CIF]
.
The compound described by Nd2Ti2O7 crystallizes in the monoclinic P2_1 space group. There are four inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 9-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(9), two equivalent O(1), and two equivalent O(2) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the third Nd site, Nd(3) is bonded in a 7-coordinate geometry to one O(11), one O(14), one O(9), two equivalent O(12), and two equivalent O(13) atoms. In the fourth Nd site, Nd(4) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(7), one O(8), and two equivalent O(14) atoms. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(3), one O(4), one O(5), one O(7), and two equivalent O(2) atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 19-44°. In the second Ti site, Ti(2) is bonded to one O(3), one O(4), one O(6), one O(8), and two equivalent O(1) atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 19-39°. In the third Ti site, Ti(3) is bonded to one O(10), one O(11), one O(14), one O(5), one O(7), and one O(9) atom to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 24-44°. In the fourth Ti site, Ti(4) is bonded to one O(10), one O(12), one O(13), one O(6), one O(8), and one O(9) atom to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 24-39°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Nd(2), two equivalent Nd(1), and two equivalent Ti(2) atoms. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Nd(2), two equivalent Nd(1), and two equivalent Ti(1) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nd(1), one Ti(1), and one Ti(2) atom. In the fourth O site, O(4) is bonded to one Nd(1), one Nd(2), one Ti(1), and one Ti(2) atom to form a mixture of distorted corner and edge-sharing ONd2Ti2 tetrahedra. In the fifth O site, O(5) is bonded to one Nd(1), one Nd(2), one Ti(1), and one Ti(3) atom to form distorted ONd2Ti2 tetrahedra that share  a cornercorner with one O(4)Nd2Ti2 tetrahedra,  a cornercorner with one O(14)Nd3Ti tetrahedra, corners with two equivalent O(6)Nd2Ti2 tetrahedra, and  an edgeedge with one O(4)Nd2Ti2 tetrahedra. In the sixth O site, O(6) is bonded to one Nd(1), one Nd(2), one Ti(2), and one Ti(4) atom to form distorted ONd2Ti2 tetrahedra that share  a cornercorner with one O(4)Nd2Ti2 tetrahedra,  a cornercorner with one O(12)Nd3Ti tetrahedra,  a cornercorner with one O(13)Nd3Ti tetrahedra, corners with two equivalent O(5)Nd2Ti2 tetrahedra, and  an edgeedge with one O(4)Nd2Ti2 tetrahedra. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Nd(2), one Nd(4), one Ti(1), and one Ti(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Nd(2), one Nd(4), one Ti(2), and one Ti(4) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Nd(1), one Nd(3), one Ti(3), and one Ti(4) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Nd(2), one Nd(4), one Ti(3), and one Ti(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nd(3), one Nd(4), and one Ti(3) atom. In the twelfth O site, O(12) is bonded to one Nd(4), two equivalent Nd(3), and one Ti(4) atom to form distorted ONd3Ti tetrahedra that share  a cornercorner with one O(6)Nd2Ti2 tetrahedra, corners with two equivalent O(12)Nd3Ti tetrahedra, corners with four equivalent O(14)Nd3Ti tetrahedra, and edges with three equivalent O(13)Nd3Ti tetrahedra. In the thirteenth O site, O(13) is bonded to one Nd(4), two equivalent Nd(3), and one Ti(4) atom to form distorted ONd3Ti tetrahedra that share  a cornercorner with one O(6)Nd2Ti2 tetrahedra, corners with two equivalent O(13)Nd3Ti tetrahedra, corners with two equivalent O(14)Nd3Ti tetrahedra,  an edgeedge with one O(14)Nd3Ti tetrahedra, and edges with three equivalent O(12)Nd3Ti tetrahedra. In the fourteenth O site, O(14) is bonded to one Nd(3), two equivalent Nd(4), and one Ti(3) atom to form distorted ONd3Ti tetrahedra that share  a cornercorner with one O(5)Nd2Ti2 tetrahedra, corners with two equivalent O(13)Nd3Ti tetrahedra, corners with two equivalent O(14)Nd3Ti tetrahedra, corners with four equivalent O(12)Nd3Ti tetrahedra, and  an edgeedge with one O(13)Nd3Ti tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Nd2Ti2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.484
_cell_length_b   7.679
_cell_length_c   13.101
_cell_angle_alpha   81.505
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   545.647
_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
  Nd  Nd0  1  0.754  0.729  0.090  1.0
  Nd  Nd1  1  0.254  0.271  0.910  1.0
  Nd  Nd2  1  0.742  0.219  0.121  1.0
  Nd  Nd3  1  0.242  0.781  0.879  1.0
  Nd  Nd4  1  0.349  0.645  0.428  1.0
  Nd  Nd5  1  0.849  0.355  0.572  1.0
  Nd  Nd6  1  0.281  0.149  0.383  1.0
  Nd  Nd7  1  0.781  0.851  0.617  1.0
  Ti  Ti8  1  0.255  0.972  0.121  1.0
  Ti  Ti9  1  0.755  0.028  0.879  1.0
  Ti  Ti10  1  0.257  0.469  0.119  1.0
  Ti  Ti11  1  0.757  0.531  0.881  1.0
  Ti  Ti12  1  0.788  0.914  0.325  1.0
  Ti  Ti13  1  0.288  0.086  0.675  1.0
  Ti  Ti14  1  0.781  0.426  0.320  1.0
  Ti  Ti15  1  0.281  0.574  0.680  1.0
  O  O16  1  0.018  0.543  0.981  1.0
  O  O17  1  0.518  0.457  0.019  1.0
  O  O18  1  0.018  0.967  0.979  1.0
  O  O19  1  0.518  0.033  0.021  1.0
  O  O20  1  0.310  0.723  0.109  1.0
  O  O21  1  0.810  0.277  0.891  1.0
  O  O22  1  0.167  0.227  0.092  1.0
  O  O23  1  0.667  0.773  0.908  1.0
  O  O24  1  0.936  0.933  0.181  1.0
  O  O25  1  0.436  0.067  0.819  1.0
  O  O26  1  0.941  0.478  0.183  1.0
  O  O27  1  0.441  0.522  0.817  1.0
  O  O28  1  0.450  0.003  0.230  1.0
  O  O29  1  0.950  0.997  0.770  1.0
  O  O30  1  0.454  0.384  0.227  1.0
  O  O31  1  0.954  0.616  0.773  1.0
  O  O32  1  0.689  0.674  0.305  1.0
  O  O33  1  0.189  0.326  0.695  1.0
  O  O34  1  0.847  0.173  0.306  1.0
  O  O35  1  0.347  0.827  0.694  1.0
  O  O36  1  0.073  0.874  0.388  1.0
  O  O37  1  0.064  0.630  0.571  1.0
  O  O38  1  0.573  0.126  0.612  1.0
  O  O39  1  0.549  0.579  0.594  1.0
  O  O40  1  0.581  0.909  0.442  1.0
  O  O41  1  0.081  0.091  0.558  1.0
  O  O42  1  0.564  0.370  0.429  1.0
  O  O43  1  0.049  0.421  0.406  1.0
[/CIF]
.