The crystal structure described by La2Ti2SiO9 crystallizes in the monoclinic C2/m space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), and four equivalent O(2) atoms. In the second La site, La(2) is bonded in a 10-coordinate geometry to one O(4), one O(6), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(7) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. In the second Ti site, Ti(2) is bonded to one O(3), one O(5), two equivalent O(2), and two equivalent O(7) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  an edgeedge with one Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. Si(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ti(2)O6 octahedra and corners with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-57°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one La(1), one La(2), one Ti(1), and one Si(1) atom. In the second O site, O(2) is bonded to one La(2), two equivalent La(1), and one Ti(2) atom to form a mixture of distorted corner and edge-sharing OLa3Ti tetrahedra. In the third O site, O(3) is bonded in a distorted single-bond geometry to one La(1), two equivalent La(2), one Ti(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one La(2) and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ti(2) and two equivalent Ti(1) atoms. In the sixth O site, O(6) is bonded in a distorted L-shaped geometry to one La(2) and two equivalent Ti(1) atoms. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to two equivalent La(2) and two equivalent Ti(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_La2Ti2SiO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.031
_cell_length_b   9.031
_cell_length_c   7.738
_cell_angle_alpha   69.942
_cell_angle_beta   69.942
_cell_angle_gamma   37.392
_symmetry_Int_Tables_number   1
_cell_volume   357.227
_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
  La  La0  1  0.788  0.788  0.307  1.0
  La  La1  1  0.212  0.212  0.693  1.0
  La  La2  1  0.894  0.894  0.694  1.0
  La  La3  1  0.106  0.106  0.306  1.0
  Ti  Ti4  1  0.759  0.241  0.000  1.0
  Ti  Ti5  1  0.581  0.581  0.553  1.0
  Ti  Ti6  1  0.419  0.419  0.447  1.0
  Ti  Ti7  1  0.241  0.759  0.000  1.0
  Si  Si8  1  0.662  0.662  0.020  1.0
  Si  Si9  1  0.338  0.338  0.980  1.0
  O  O10  1  0.626  0.140  0.013  1.0
  O  O11  1  0.421  0.901  0.517  1.0
  O  O12  1  0.655  0.655  0.235  1.0
  O  O13  1  0.756  0.756  0.866  1.0
  O  O14  1  0.472  0.472  0.187  1.0
  O  O15  1  0.345  0.345  0.765  1.0
  O  O16  1  0.976  0.976  0.178  1.0
  O  O17  1  0.277  0.723  0.500  1.0
  O  O18  1  0.901  0.421  0.517  1.0
  O  O19  1  0.374  0.860  0.987  1.0
  O  O20  1  0.140  0.626  0.013  1.0
  O  O21  1  0.528  0.528  0.813  1.0
  O  O22  1  0.244  0.244  0.134  1.0
  O  O23  1  0.579  0.099  0.483  1.0
  O  O24  1  0.024  0.024  0.822  1.0
  O  O25  1  0.723  0.277  0.500  1.0
  O  O26  1  0.099  0.579  0.483  1.0
  O  O27  1  0.860  0.374  0.987  1.0
[/CIF]
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The crystal structure described by La2Ti2SiO9 crystallizes in the monoclinic C2/m space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), and four equivalent O(2) atoms. In the second La site, La(2) is bonded in a 10-coordinate geometry to one O(4), one O(6), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(7) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. In the second Ti site, Ti(2) is bonded to one O(3), one O(5), two equivalent O(2), and two equivalent O(7) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  an edgeedge with one Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. Si(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ti(2)O6 octahedra and corners with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-57°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one La(1), one La(2), one Ti(1), and one Si(1) atom. In the second O site, O(2) is bonded to one La(2), two equivalent La(1), and one Ti(2) atom to form a mixture of distorted corner and edge-sharing OLa3Ti tetrahedra. In the third O site, O(3) is bonded in a distorted single-bond geometry to one La(1), two equivalent La(2), one Ti(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one La(2) and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ti(2) and two equivalent Ti(1) atoms. In the sixth O site, O(6) is bonded in a distorted L-shaped geometry to one La(2) and two equivalent Ti(1) atoms. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to two equivalent La(2) and two equivalent Ti(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_La2Ti2SiO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.031
_cell_length_b   9.031
_cell_length_c   7.738
_cell_angle_alpha   69.942
_cell_angle_beta   69.942
_cell_angle_gamma   37.392
_symmetry_Int_Tables_number   1
_cell_volume   357.227
_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
  La  La0  1  0.788  0.788  0.307  1.0
  La  La1  1  0.212  0.212  0.693  1.0
  La  La2  1  0.894  0.894  0.694  1.0
  La  La3  1  0.106  0.106  0.306  1.0
  Ti  Ti4  1  0.759  0.241  0.000  1.0
  Ti  Ti5  1  0.581  0.581  0.553  1.0
  Ti  Ti6  1  0.419  0.419  0.447  1.0
  Ti  Ti7  1  0.241  0.759  0.000  1.0
  Si  Si8  1  0.662  0.662  0.020  1.0
  Si  Si9  1  0.338  0.338  0.980  1.0
  O  O10  1  0.626  0.140  0.013  1.0
  O  O11  1  0.421  0.901  0.517  1.0
  O  O12  1  0.655  0.655  0.235  1.0
  O  O13  1  0.756  0.756  0.866  1.0
  O  O14  1  0.472  0.472  0.187  1.0
  O  O15  1  0.345  0.345  0.765  1.0
  O  O16  1  0.976  0.976  0.178  1.0
  O  O17  1  0.277  0.723  0.500  1.0
  O  O18  1  0.901  0.421  0.517  1.0
  O  O19  1  0.374  0.860  0.987  1.0
  O  O20  1  0.140  0.626  0.013  1.0
  O  O21  1  0.528  0.528  0.813  1.0
  O  O22  1  0.244  0.244  0.134  1.0
  O  O23  1  0.579  0.099  0.483  1.0
  O  O24  1  0.024  0.024  0.822  1.0
  O  O25  1  0.723  0.277  0.500  1.0
  O  O26  1  0.099  0.579  0.483  1.0
  O  O27  1  0.860  0.374  0.987  1.0
[/CIF]
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