The compound described by Li3FeSi2O7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 3-coordinate geometry to one O(1), one O(3), and one O(4) atom. In the second Li site, Li(2) is bonded to one O(2), two equivalent O(1), and two equivalent O(4) atoms to form distorted LiO5 square pyramids that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Fe(1)O6 octahedra. Fe(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Li(2)O5 square pyramids. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Li(2)O5 square pyramids, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-56°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2FeSi trigonal pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to one Li(2) and two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one Si(1) atom. In the fourth O site, O(4) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form a mixture of edge and corner-sharing OLi2FeSi tetrahedra. is represented by the CIF file [CIF]
data_Li3FeSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.027
_cell_length_b   8.964
_cell_length_c   12.488
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   562.749
_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
  Li  Li0  1  0.034  0.338  0.091  1.0
  Li  Li1  1  0.034  0.338  0.409  1.0
  Li  Li2  1  0.031  0.015  0.250  1.0
  Li  Li3  1  0.469  0.515  0.250  1.0
  Li  Li4  1  0.466  0.838  0.091  1.0
  Li  Li5  1  0.466  0.838  0.409  1.0
  Li  Li6  1  0.534  0.162  0.591  1.0
  Li  Li7  1  0.534  0.162  0.909  1.0
  Li  Li8  1  0.531  0.485  0.750  1.0
  Li  Li9  1  0.969  0.985  0.750  1.0
  Li  Li10  1  0.966  0.662  0.909  1.0
  Li  Li11  1  0.966  0.662  0.591  1.0
  Fe  Fe12  1  0.000  0.000  0.000  1.0
  Fe  Fe13  1  0.000  0.000  0.500  1.0
  Fe  Fe14  1  0.500  0.500  0.500  1.0
  Fe  Fe15  1  0.500  0.500  0.000  1.0
  Si  Si16  1  0.009  0.318  0.631  1.0
  Si  Si17  1  0.009  0.318  0.869  1.0
  Si  Si18  1  0.491  0.818  0.631  1.0
  Si  Si19  1  0.491  0.818  0.869  1.0
  Si  Si20  1  0.509  0.182  0.131  1.0
  Si  Si21  1  0.509  0.182  0.369  1.0
  Si  Si22  1  0.991  0.682  0.131  1.0
  Si  Si23  1  0.991  0.682  0.369  1.0
  O  O24  1  0.069  0.860  0.129  1.0
  O  O25  1  0.069  0.860  0.371  1.0
  O  O26  1  0.090  0.612  0.250  1.0
  O  O27  1  0.166  0.601  0.038  1.0
  O  O28  1  0.166  0.601  0.462  1.0
  O  O29  1  0.174  0.853  0.616  1.0
  O  O30  1  0.174  0.853  0.884  1.0
  O  O31  1  0.326  0.353  0.616  1.0
  O  O32  1  0.326  0.353  0.884  1.0
  O  O33  1  0.334  0.101  0.038  1.0
  O  O34  1  0.334  0.101  0.462  1.0
  O  O35  1  0.410  0.112  0.250  1.0
  O  O36  1  0.431  0.360  0.129  1.0
  O  O37  1  0.431  0.360  0.371  1.0
  O  O38  1  0.569  0.640  0.629  1.0
  O  O39  1  0.569  0.640  0.871  1.0
  O  O40  1  0.590  0.888  0.750  1.0
  O  O41  1  0.666  0.899  0.538  1.0
  O  O42  1  0.666  0.899  0.962  1.0
  O  O43  1  0.674  0.647  0.116  1.0
  O  O44  1  0.674  0.647  0.384  1.0
  O  O45  1  0.826  0.147  0.384  1.0
  O  O46  1  0.826  0.147  0.116  1.0
  O  O47  1  0.834  0.399  0.538  1.0
  O  O48  1  0.834  0.399  0.962  1.0
  O  O49  1  0.910  0.388  0.750  1.0
  O  O50  1  0.931  0.140  0.629  1.0
  O  O51  1  0.931  0.140  0.871  1.0
[/CIF]
.
The compound described by Li3FeSi2O7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 3-coordinate geometry to one O(1), one O(3), and one O(4) atom. In the second Li site, Li(2) is bonded to one O(2), two equivalent O(1), and two equivalent O(4) atoms to form distorted LiO5 square pyramids that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Fe(1)O6 octahedra. Fe(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Li(2)O5 square pyramids. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Li(2)O5 square pyramids, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-56°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2FeSi trigonal pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to one Li(2) and two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one Si(1) atom. In the fourth O site, O(4) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form a mixture of edge and corner-sharing OLi2FeSi tetrahedra. is represented by the CIF file [CIF]
data_Li3FeSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.027
_cell_length_b   8.964
_cell_length_c   12.488
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   562.749
_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
  Li  Li0  1  0.034  0.338  0.091  1.0
  Li  Li1  1  0.034  0.338  0.409  1.0
  Li  Li2  1  0.031  0.015  0.250  1.0
  Li  Li3  1  0.469  0.515  0.250  1.0
  Li  Li4  1  0.466  0.838  0.091  1.0
  Li  Li5  1  0.466  0.838  0.409  1.0
  Li  Li6  1  0.534  0.162  0.591  1.0
  Li  Li7  1  0.534  0.162  0.909  1.0
  Li  Li8  1  0.531  0.485  0.750  1.0
  Li  Li9  1  0.969  0.985  0.750  1.0
  Li  Li10  1  0.966  0.662  0.909  1.0
  Li  Li11  1  0.966  0.662  0.591  1.0
  Fe  Fe12  1  0.000  0.000  0.000  1.0
  Fe  Fe13  1  0.000  0.000  0.500  1.0
  Fe  Fe14  1  0.500  0.500  0.500  1.0
  Fe  Fe15  1  0.500  0.500  0.000  1.0
  Si  Si16  1  0.009  0.318  0.631  1.0
  Si  Si17  1  0.009  0.318  0.869  1.0
  Si  Si18  1  0.491  0.818  0.631  1.0
  Si  Si19  1  0.491  0.818  0.869  1.0
  Si  Si20  1  0.509  0.182  0.131  1.0
  Si  Si21  1  0.509  0.182  0.369  1.0
  Si  Si22  1  0.991  0.682  0.131  1.0
  Si  Si23  1  0.991  0.682  0.369  1.0
  O  O24  1  0.069  0.860  0.129  1.0
  O  O25  1  0.069  0.860  0.371  1.0
  O  O26  1  0.090  0.612  0.250  1.0
  O  O27  1  0.166  0.601  0.038  1.0
  O  O28  1  0.166  0.601  0.462  1.0
  O  O29  1  0.174  0.853  0.616  1.0
  O  O30  1  0.174  0.853  0.884  1.0
  O  O31  1  0.326  0.353  0.616  1.0
  O  O32  1  0.326  0.353  0.884  1.0
  O  O33  1  0.334  0.101  0.038  1.0
  O  O34  1  0.334  0.101  0.462  1.0
  O  O35  1  0.410  0.112  0.250  1.0
  O  O36  1  0.431  0.360  0.129  1.0
  O  O37  1  0.431  0.360  0.371  1.0
  O  O38  1  0.569  0.640  0.629  1.0
  O  O39  1  0.569  0.640  0.871  1.0
  O  O40  1  0.590  0.888  0.750  1.0
  O  O41  1  0.666  0.899  0.538  1.0
  O  O42  1  0.666  0.899  0.962  1.0
  O  O43  1  0.674  0.647  0.116  1.0
  O  O44  1  0.674  0.647  0.384  1.0
  O  O45  1  0.826  0.147  0.384  1.0
  O  O46  1  0.826  0.147  0.116  1.0
  O  O47  1  0.834  0.399  0.538  1.0
  O  O48  1  0.834  0.399  0.962  1.0
  O  O49  1  0.910  0.388  0.750  1.0
  O  O50  1  0.931  0.140  0.629  1.0
  O  O51  1  0.931  0.140  0.871  1.0
[/CIF]
.