The compound described by La2SiO5 crystallizes in the monoclinic C2/c space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to one O(1), one O(2), one O(5), one O(6), and two equivalent O(4) atoms to form distorted LaO6 octahedra that share  a cornercorner with one La(2)O6 octahedra,  a cornercorner with one La(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one La(1)O6 octahedra,  an edgeedge with one La(3)O6 octahedra, edges with two equivalent La(2)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-54°. In the second La site, La(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(8) atom to form LaO6 octahedra that share  a cornercorner with one La(1)O6 octahedra,  a cornercorner with one La(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, edges with two equivalent La(1)O6 octahedra, and edges with two equivalent La(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. In the third La site, La(3) is bonded to one O(3), one O(4), one O(6), one O(8), and two equivalent O(7) atoms to form distorted LaO6 octahedra that share  a cornercorner with one La(1)O6 octahedra,  a cornercorner with one La(3)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one La(1)O6 octahedra,  an edgeedge with one La(3)O6 octahedra, and edges with two equivalent La(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-61°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one La(1)O6 octahedra, corners with two equivalent La(3)O6 octahedra, corners with three equivalent La(2)O6 octahedra, and  an edgeedge with one La(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-58°. In the second Si site, Si(2) is bonded to two equivalent O(5) and two equivalent O(7) atoms to form SiO4 tetrahedra that share corners with two equivalent La(1)O6 octahedra, corners with two equivalent La(2)O6 octahedra, and corners with four equivalent La(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-56°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one La(1), one La(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one La(1), one La(2), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one La(2), one La(3), and one Si(1) atom. In the fourth O site, O(4) is bonded to one La(2), one La(3), and two equivalent La(1) atoms to form edge-sharing OLa4 tetrahedra. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one La(1), one La(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one La(1), one La(3), and one Si(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent La(3) and one Si(2) atom. In the eighth O site, O(8) is bonded to two equivalent La(2) and two equivalent La(3) atoms to form edge-sharing OLa4 tetrahedra. is represented by the CIF file [CIF]
data_La2SiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.301
_cell_length_b   8.301
_cell_length_c   11.794
_cell_angle_alpha   84.125
_cell_angle_beta   84.125
_cell_angle_gamma   91.139
_symmetry_Int_Tables_number   1
_cell_volume   803.694
_cell_formula_units_Z   6
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  0.714  0.002  0.931  1.0
  La  La1  1  0.002  0.714  0.431  1.0
  La  La2  1  0.360  0.020  0.745  1.0
  La  La3  1  0.020  0.360  0.245  1.0
  La  La4  1  0.385  0.663  0.570  1.0
  La  La5  1  0.337  0.615  0.930  1.0
  La  La6  1  0.663  0.385  0.070  1.0
  La  La7  1  0.615  0.337  0.430  1.0
  La  La8  1  0.980  0.640  0.755  1.0
  La  La9  1  0.640  0.980  0.255  1.0
  La  La10  1  0.998  0.286  0.569  1.0
  La  La11  1  0.286  0.998  0.069  1.0
  Si  Si12  1  0.731  0.928  0.551  1.0
  Si  Si13  1  0.928  0.731  0.051  1.0
  Si  Si14  1  0.632  0.368  0.750  1.0
  Si  Si15  1  0.368  0.632  0.250  1.0
  Si  Si16  1  0.072  0.269  0.949  1.0
  Si  Si17  1  0.269  0.072  0.449  1.0
  O  O18  1  0.875  0.835  0.618  1.0
  O  O19  1  0.835  0.875  0.118  1.0
  O  O20  1  0.851  0.745  0.925  1.0
  O  O21  1  0.745  0.851  0.425  1.0
  O  O22  1  0.550  0.883  0.618  1.0
  O  O23  1  0.448  0.884  0.923  1.0
  O  O24  1  0.883  0.550  0.118  1.0
  O  O25  1  0.884  0.448  0.423  1.0
  O  O26  1  0.830  0.401  0.718  1.0
  O  O27  1  0.401  0.830  0.218  1.0
  O  O28  1  0.875  0.236  0.969  1.0
  O  O29  1  0.568  0.458  0.865  1.0
  O  O30  1  0.236  0.875  0.469  1.0
  O  O31  1  0.257  0.743  0.750  1.0
  O  O32  1  0.458  0.568  0.365  1.0
  O  O33  1  0.542  0.432  0.635  1.0
  O  O34  1  0.743  0.257  0.250  1.0
  O  O35  1  0.764  0.125  0.531  1.0
  O  O36  1  0.432  0.542  0.135  1.0
  O  O37  1  0.125  0.764  0.031  1.0
  O  O38  1  0.599  0.170  0.782  1.0
  O  O39  1  0.170  0.599  0.282  1.0
  O  O40  1  0.116  0.552  0.577  1.0
  O  O41  1  0.117  0.450  0.882  1.0
  O  O42  1  0.552  0.116  0.077  1.0
  O  O43  1  0.450  0.117  0.382  1.0
  O  O44  1  0.255  0.149  0.575  1.0
  O  O45  1  0.149  0.255  0.075  1.0
  O  O46  1  0.165  0.125  0.882  1.0
  O  O47  1  0.125  0.165  0.382  1.0
[/CIF]
.
The compound described by La2SiO5 crystallizes in the monoclinic C2/c space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to one O(1), one O(2), one O(5), one O(6), and two equivalent O(4) atoms to form distorted LaO6 octahedra that share  a cornercorner with one La(2)O6 octahedra,  a cornercorner with one La(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one La(1)O6 octahedra,  an edgeedge with one La(3)O6 octahedra, edges with two equivalent La(2)O6 octahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-54°. In the second La site, La(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(8) atom to form LaO6 octahedra that share  a cornercorner with one La(1)O6 octahedra,  a cornercorner with one La(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, edges with two equivalent La(1)O6 octahedra, and edges with two equivalent La(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. In the third La site, La(3) is bonded to one O(3), one O(4), one O(6), one O(8), and two equivalent O(7) atoms to form distorted LaO6 octahedra that share  a cornercorner with one La(1)O6 octahedra,  a cornercorner with one La(3)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one La(1)O6 octahedra,  an edgeedge with one La(3)O6 octahedra, and edges with two equivalent La(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-61°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one La(1)O6 octahedra, corners with two equivalent La(3)O6 octahedra, corners with three equivalent La(2)O6 octahedra, and  an edgeedge with one La(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-58°. In the second Si site, Si(2) is bonded to two equivalent O(5) and two equivalent O(7) atoms to form SiO4 tetrahedra that share corners with two equivalent La(1)O6 octahedra, corners with two equivalent La(2)O6 octahedra, and corners with four equivalent La(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-56°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one La(1), one La(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one La(1), one La(2), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one La(2), one La(3), and one Si(1) atom. In the fourth O site, O(4) is bonded to one La(2), one La(3), and two equivalent La(1) atoms to form edge-sharing OLa4 tetrahedra. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one La(1), one La(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one La(1), one La(3), and one Si(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent La(3) and one Si(2) atom. In the eighth O site, O(8) is bonded to two equivalent La(2) and two equivalent La(3) atoms to form edge-sharing OLa4 tetrahedra. is represented by the CIF file [CIF]
data_La2SiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.301
_cell_length_b   8.301
_cell_length_c   11.794
_cell_angle_alpha   84.125
_cell_angle_beta   84.125
_cell_angle_gamma   91.139
_symmetry_Int_Tables_number   1
_cell_volume   803.694
_cell_formula_units_Z   6
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  0.714  0.002  0.931  1.0
  La  La1  1  0.002  0.714  0.431  1.0
  La  La2  1  0.360  0.020  0.745  1.0
  La  La3  1  0.020  0.360  0.245  1.0
  La  La4  1  0.385  0.663  0.570  1.0
  La  La5  1  0.337  0.615  0.930  1.0
  La  La6  1  0.663  0.385  0.070  1.0
  La  La7  1  0.615  0.337  0.430  1.0
  La  La8  1  0.980  0.640  0.755  1.0
  La  La9  1  0.640  0.980  0.255  1.0
  La  La10  1  0.998  0.286  0.569  1.0
  La  La11  1  0.286  0.998  0.069  1.0
  Si  Si12  1  0.731  0.928  0.551  1.0
  Si  Si13  1  0.928  0.731  0.051  1.0
  Si  Si14  1  0.632  0.368  0.750  1.0
  Si  Si15  1  0.368  0.632  0.250  1.0
  Si  Si16  1  0.072  0.269  0.949  1.0
  Si  Si17  1  0.269  0.072  0.449  1.0
  O  O18  1  0.875  0.835  0.618  1.0
  O  O19  1  0.835  0.875  0.118  1.0
  O  O20  1  0.851  0.745  0.925  1.0
  O  O21  1  0.745  0.851  0.425  1.0
  O  O22  1  0.550  0.883  0.618  1.0
  O  O23  1  0.448  0.884  0.923  1.0
  O  O24  1  0.883  0.550  0.118  1.0
  O  O25  1  0.884  0.448  0.423  1.0
  O  O26  1  0.830  0.401  0.718  1.0
  O  O27  1  0.401  0.830  0.218  1.0
  O  O28  1  0.875  0.236  0.969  1.0
  O  O29  1  0.568  0.458  0.865  1.0
  O  O30  1  0.236  0.875  0.469  1.0
  O  O31  1  0.257  0.743  0.750  1.0
  O  O32  1  0.458  0.568  0.365  1.0
  O  O33  1  0.542  0.432  0.635  1.0
  O  O34  1  0.743  0.257  0.250  1.0
  O  O35  1  0.764  0.125  0.531  1.0
  O  O36  1  0.432  0.542  0.135  1.0
  O  O37  1  0.125  0.764  0.031  1.0
  O  O38  1  0.599  0.170  0.782  1.0
  O  O39  1  0.170  0.599  0.282  1.0
  O  O40  1  0.116  0.552  0.577  1.0
  O  O41  1  0.117  0.450  0.882  1.0
  O  O42  1  0.552  0.116  0.077  1.0
  O  O43  1  0.450  0.117  0.382  1.0
  O  O44  1  0.255  0.149  0.575  1.0
  O  O45  1  0.149  0.255  0.075  1.0
  O  O46  1  0.165  0.125  0.882  1.0
  O  O47  1  0.125  0.165  0.382  1.0
[/CIF]
.