The material described by Na2Ti2Si4O13 is Esseneite-like structured and crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 8-coordinate geometry to one O(4), one O(5), one O(6), one O(7), two equivalent O(2), and two equivalent O(3) atoms. Ti(1) is bonded to one O(5), one O(7), two equivalent O(4), and two equivalent O(6) atoms to form TiO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(5), one O(6), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Ti(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-55°. In the second Si site, Si(2) is bonded to one O(1), one O(7), and two equivalent O(2) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra and corners with three equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 31°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Na(1) and two equivalent Si(2) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1) and two equivalent Si(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Na(1) and two equivalent Ti(1) atoms. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1), one Ti(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), two equivalent Ti(1), and one Si(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one Ti(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Ti2Si4O13
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.169
_cell_length_b   13.169
_cell_length_c   5.262
_cell_angle_alpha   80.832
_cell_angle_beta   80.832
_cell_angle_gamma   38.806
_symmetry_Int_Tables_number   1
_cell_volume   563.730
_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  0.049  0.653  0.300  1.0
  Na  Na1  1  0.653  0.049  0.800  1.0
  Na  Na2  1  0.951  0.347  0.700  1.0
  Na  Na3  1  0.347  0.951  0.200  1.0
  Ti  Ti4  1  0.742  0.558  0.212  1.0
  Ti  Ti5  1  0.558  0.742  0.712  1.0
  Ti  Ti6  1  0.258  0.442  0.788  1.0
  Ti  Ti7  1  0.442  0.258  0.288  1.0
  Si  Si8  1  0.859  0.674  0.774  1.0
  Si  Si9  1  0.674  0.859  0.274  1.0
  Si  Si10  1  0.141  0.326  0.226  1.0
  Si  Si11  1  0.326  0.141  0.726  1.0
  Si  Si12  1  0.038  0.834  0.779  1.0
  Si  Si13  1  0.834  0.038  0.279  1.0
  Si  Si14  1  0.962  0.166  0.221  1.0
  Si  Si15  1  0.166  0.962  0.721  1.0
  O  O16  1  0.148  0.852  0.750  1.0
  O  O17  1  0.852  0.148  0.250  1.0
  O  O18  1  0.958  0.888  0.501  1.0
  O  O19  1  0.888  0.958  0.001  1.0
  O  O20  1  0.042  0.112  0.499  1.0
  O  O21  1  0.112  0.042  0.999  1.0
  O  O22  1  0.788  0.796  0.508  1.0
  O  O23  1  0.796  0.788  0.008  1.0
  O  O24  1  0.212  0.204  0.492  1.0
  O  O25  1  0.204  0.212  0.992  1.0
  O  O26  1  0.683  0.551  0.544  1.0
  O  O27  1  0.551  0.683  0.044  1.0
  O  O28  1  0.317  0.449  0.456  1.0
  O  O29  1  0.449  0.317  0.956  1.0
  O  O30  1  0.946  0.468  0.271  1.0
  O  O31  1  0.468  0.946  0.771  1.0
  O  O32  1  0.054  0.532  0.729  1.0
  O  O33  1  0.532  0.054  0.229  1.0
  O  O34  1  0.783  0.618  0.829  1.0
  O  O35  1  0.618  0.783  0.329  1.0
  O  O36  1  0.217  0.382  0.171  1.0
  O  O37  1  0.382  0.217  0.671  1.0
  O  O38  1  0.862  0.346  0.128  1.0
  O  O39  1  0.346  0.862  0.628  1.0
  O  O40  1  0.138  0.654  0.872  1.0
  O  O41  1  0.654  0.138  0.372  1.0
[/CIF]
.
The material described by Na2Ti2Si4O13 is Esseneite-like structured and crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 8-coordinate geometry to one O(4), one O(5), one O(6), one O(7), two equivalent O(2), and two equivalent O(3) atoms. Ti(1) is bonded to one O(5), one O(7), two equivalent O(4), and two equivalent O(6) atoms to form TiO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(5), one O(6), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Ti(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-55°. In the second Si site, Si(2) is bonded to one O(1), one O(7), and two equivalent O(2) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra and corners with three equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 31°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Na(1) and two equivalent Si(2) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1) and two equivalent Si(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Na(1) and two equivalent Ti(1) atoms. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1), one Ti(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), two equivalent Ti(1), and one Si(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(1), one Ti(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Ti2Si4O13
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.169
_cell_length_b   13.169
_cell_length_c   5.262
_cell_angle_alpha   80.832
_cell_angle_beta   80.832
_cell_angle_gamma   38.806
_symmetry_Int_Tables_number   1
_cell_volume   563.730
_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  0.049  0.653  0.300  1.0
  Na  Na1  1  0.653  0.049  0.800  1.0
  Na  Na2  1  0.951  0.347  0.700  1.0
  Na  Na3  1  0.347  0.951  0.200  1.0
  Ti  Ti4  1  0.742  0.558  0.212  1.0
  Ti  Ti5  1  0.558  0.742  0.712  1.0
  Ti  Ti6  1  0.258  0.442  0.788  1.0
  Ti  Ti7  1  0.442  0.258  0.288  1.0
  Si  Si8  1  0.859  0.674  0.774  1.0
  Si  Si9  1  0.674  0.859  0.274  1.0
  Si  Si10  1  0.141  0.326  0.226  1.0
  Si  Si11  1  0.326  0.141  0.726  1.0
  Si  Si12  1  0.038  0.834  0.779  1.0
  Si  Si13  1  0.834  0.038  0.279  1.0
  Si  Si14  1  0.962  0.166  0.221  1.0
  Si  Si15  1  0.166  0.962  0.721  1.0
  O  O16  1  0.148  0.852  0.750  1.0
  O  O17  1  0.852  0.148  0.250  1.0
  O  O18  1  0.958  0.888  0.501  1.0
  O  O19  1  0.888  0.958  0.001  1.0
  O  O20  1  0.042  0.112  0.499  1.0
  O  O21  1  0.112  0.042  0.999  1.0
  O  O22  1  0.788  0.796  0.508  1.0
  O  O23  1  0.796  0.788  0.008  1.0
  O  O24  1  0.212  0.204  0.492  1.0
  O  O25  1  0.204  0.212  0.992  1.0
  O  O26  1  0.683  0.551  0.544  1.0
  O  O27  1  0.551  0.683  0.044  1.0
  O  O28  1  0.317  0.449  0.456  1.0
  O  O29  1  0.449  0.317  0.956  1.0
  O  O30  1  0.946  0.468  0.271  1.0
  O  O31  1  0.468  0.946  0.771  1.0
  O  O32  1  0.054  0.532  0.729  1.0
  O  O33  1  0.532  0.054  0.229  1.0
  O  O34  1  0.783  0.618  0.829  1.0
  O  O35  1  0.618  0.783  0.329  1.0
  O  O36  1  0.217  0.382  0.171  1.0
  O  O37  1  0.382  0.217  0.671  1.0
  O  O38  1  0.862  0.346  0.128  1.0
  O  O39  1  0.346  0.862  0.628  1.0
  O  O40  1  0.138  0.654  0.872  1.0
  O  O41  1  0.654  0.138  0.372  1.0
[/CIF]
.