The compound described by Na6Ti2O7 crystallizes in the monoclinic P2/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded to one O(3), two equivalent O(1), and three equivalent O(2) atoms to form distorted NaO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with two equivalent Ti(1)O4 tetrahedra, edges with three equivalent Na(2)O6 octahedra, and edges with two equivalent Ti(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the third Na site, Na(3) is bonded in a rectangular see-saw-like geometry to one O(1), one O(4), and two equivalent O(3) atoms. Ti(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form TiO4 tetrahedra that share corners with two equivalent Na(2)O6 octahedra,  a cornercorner with one Ti(1)O4 tetrahedra, and edges with two equivalent Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-70°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(3), two equivalent Na(1), two equivalent Na(2), and one Ti(1) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Na(1), three equivalent Na(2), and one Ti(1) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), two equivalent Na(3), and one Ti(1) atom to form distorted ONa4Ti trigonal bipyramids that share  a cornercorner with one O(4)Na2Ti2 tetrahedra,  an edgeedge with one O(4)Na2Ti2 tetrahedra, and  an edgeedge with one O(3)Na4Ti trigonal bipyramid. In the fourth O site, O(4) is bonded to two equivalent Na(3) and two equivalent Ti(1) atoms to form a mixture of distorted corner and edge-sharing ONa2Ti2 tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na6Ti2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.216
_cell_length_b   8.829
_cell_length_c   10.231
_cell_angle_alpha   62.738
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   418.812
_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
  Na  Na0  1  0.232  0.336  0.879  1.0
  Na  Na1  1  0.775  0.573  0.862  1.0
  Na  Na2  1  0.802  0.065  0.847  1.0
  Na  Na3  1  0.775  0.427  0.638  1.0
  Na  Na4  1  0.232  0.664  0.621  1.0
  Na  Na5  1  0.802  0.935  0.653  1.0
  Na  Na6  1  0.198  0.065  0.347  1.0
  Na  Na7  1  0.768  0.336  0.379  1.0
  Na  Na8  1  0.225  0.573  0.362  1.0
  Na  Na9  1  0.198  0.935  0.153  1.0
  Na  Na10  1  0.225  0.427  0.138  1.0
  Na  Na11  1  0.768  0.664  0.121  1.0
  Ti  Ti12  1  0.305  0.787  0.896  1.0
  Ti  Ti13  1  0.305  0.213  0.604  1.0
  Ti  Ti14  1  0.695  0.787  0.396  1.0
  Ti  Ti15  1  0.695  0.213  0.104  1.0
  O  O16  1  0.788  0.275  0.914  1.0
  O  O17  1  0.230  0.610  0.860  1.0
  O  O18  1  0.647  0.809  0.887  1.0
  O  O19  1  0.230  0.390  0.640  1.0
  O  O20  1  0.169  0.000  0.750  1.0
  O  O21  1  0.788  0.725  0.586  1.0
  O  O22  1  0.647  0.191  0.613  1.0
  O  O23  1  0.353  0.809  0.387  1.0
  O  O24  1  0.212  0.275  0.414  1.0
  O  O25  1  0.831  0.000  0.250  1.0
  O  O26  1  0.770  0.610  0.360  1.0
  O  O27  1  0.353  0.191  0.113  1.0
  O  O28  1  0.770  0.390  0.140  1.0
  O  O29  1  0.212  0.725  0.086  1.0
[/CIF]
.
The compound described by Na6Ti2O7 crystallizes in the monoclinic P2/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded to one O(3), two equivalent O(1), and three equivalent O(2) atoms to form distorted NaO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with two equivalent Ti(1)O4 tetrahedra, edges with three equivalent Na(2)O6 octahedra, and edges with two equivalent Ti(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the third Na site, Na(3) is bonded in a rectangular see-saw-like geometry to one O(1), one O(4), and two equivalent O(3) atoms. Ti(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form TiO4 tetrahedra that share corners with two equivalent Na(2)O6 octahedra,  a cornercorner with one Ti(1)O4 tetrahedra, and edges with two equivalent Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-70°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(3), two equivalent Na(1), two equivalent Na(2), and one Ti(1) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Na(1), three equivalent Na(2), and one Ti(1) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), two equivalent Na(3), and one Ti(1) atom to form distorted ONa4Ti trigonal bipyramids that share  a cornercorner with one O(4)Na2Ti2 tetrahedra,  an edgeedge with one O(4)Na2Ti2 tetrahedra, and  an edgeedge with one O(3)Na4Ti trigonal bipyramid. In the fourth O site, O(4) is bonded to two equivalent Na(3) and two equivalent Ti(1) atoms to form a mixture of distorted corner and edge-sharing ONa2Ti2 tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na6Ti2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.216
_cell_length_b   8.829
_cell_length_c   10.231
_cell_angle_alpha   62.738
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   418.812
_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
  Na  Na0  1  0.232  0.336  0.879  1.0
  Na  Na1  1  0.775  0.573  0.862  1.0
  Na  Na2  1  0.802  0.065  0.847  1.0
  Na  Na3  1  0.775  0.427  0.638  1.0
  Na  Na4  1  0.232  0.664  0.621  1.0
  Na  Na5  1  0.802  0.935  0.653  1.0
  Na  Na6  1  0.198  0.065  0.347  1.0
  Na  Na7  1  0.768  0.336  0.379  1.0
  Na  Na8  1  0.225  0.573  0.362  1.0
  Na  Na9  1  0.198  0.935  0.153  1.0
  Na  Na10  1  0.225  0.427  0.138  1.0
  Na  Na11  1  0.768  0.664  0.121  1.0
  Ti  Ti12  1  0.305  0.787  0.896  1.0
  Ti  Ti13  1  0.305  0.213  0.604  1.0
  Ti  Ti14  1  0.695  0.787  0.396  1.0
  Ti  Ti15  1  0.695  0.213  0.104  1.0
  O  O16  1  0.788  0.275  0.914  1.0
  O  O17  1  0.230  0.610  0.860  1.0
  O  O18  1  0.647  0.809  0.887  1.0
  O  O19  1  0.230  0.390  0.640  1.0
  O  O20  1  0.169  0.000  0.750  1.0
  O  O21  1  0.788  0.725  0.586  1.0
  O  O22  1  0.647  0.191  0.613  1.0
  O  O23  1  0.353  0.809  0.387  1.0
  O  O24  1  0.212  0.275  0.414  1.0
  O  O25  1  0.831  0.000  0.250  1.0
  O  O26  1  0.770  0.610  0.360  1.0
  O  O27  1  0.353  0.191  0.113  1.0
  O  O28  1  0.770  0.390  0.140  1.0
  O  O29  1  0.212  0.725  0.086  1.0
[/CIF]
.