The compound described by KNbSi2O7 crystallizes in the tetragonal P4bm space group. K(1) is bonded in a 12-coordinate geometry to one O(4), one O(5), two equivalent O(7), four equivalent O(1), and four equivalent O(2) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(6), one O(7), and four equivalent O(1) atoms to form distorted NbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedra are not tilted. In the second Nb site, Nb(2) is bonded to one O(6), one O(7), and four equivalent O(2) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedra are not tilted. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 31°. In the second Si site, Si(2) is bonded to one O(3), one O(5), and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Nb(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 18°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the second O site, O(7) is bonded in a distorted linear geometry to four equivalent K(1), one Nb(1), and one Nb(2) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), one Nb(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to two equivalent K(1), one Nb(2), and one Si(2) atom. In the fifth O site, O(3) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(1) atoms. In the seventh O site, O(5) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(2) atoms. is represented by the CIF file [CIF]
data_KNbSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.877
_cell_length_b   8.877
_cell_length_c   8.274
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   652.088
_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
  K  K0  1  0.178  0.678  0.992  1.0
  K  K1  1  0.678  0.822  0.992  1.0
  K  K2  1  0.822  0.322  0.992  1.0
  K  K3  1  0.322  0.178  0.992  1.0
  Nb  Nb4  1  0.500  0.500  0.720  1.0
  Nb  Nb5  1  0.500  0.500  0.218  1.0
  Nb  Nb6  1  0.000  0.000  0.720  1.0
  Nb  Nb7  1  0.000  0.000  0.218  1.0
  Si  Si8  1  0.124  0.376  0.693  1.0
  Si  Si9  1  0.877  0.623  0.303  1.0
  Si  Si10  1  0.377  0.877  0.303  1.0
  Si  Si11  1  0.623  0.123  0.303  1.0
  Si  Si12  1  0.624  0.124  0.693  1.0
  Si  Si13  1  0.376  0.876  0.693  1.0
  Si  Si14  1  0.876  0.624  0.693  1.0
  Si  Si15  1  0.123  0.377  0.303  1.0
  O  O16  1  0.423  0.712  0.763  1.0
  O  O17  1  0.924  0.787  0.233  1.0
  O  O18  1  0.077  0.212  0.763  1.0
  O  O19  1  0.288  0.423  0.763  1.0
  O  O20  1  0.576  0.287  0.233  1.0
  O  O21  1  0.788  0.077  0.763  1.0
  O  O22  1  0.287  0.424  0.233  1.0
  O  O23  1  0.620  0.120  0.498  1.0
  O  O24  1  0.787  0.076  0.233  1.0
  O  O25  1  0.120  0.380  0.498  1.0
  O  O26  1  0.000  0.500  0.764  1.0
  O  O27  1  0.000  0.500  0.232  1.0
  O  O28  1  0.380  0.880  0.498  1.0
  O  O29  1  0.500  0.000  0.764  1.0
  O  O30  1  0.880  0.620  0.498  1.0
  O  O31  1  0.923  0.788  0.763  1.0
  O  O32  1  0.076  0.213  0.233  1.0
  O  O33  1  0.424  0.713  0.233  1.0
  O  O34  1  0.213  0.924  0.233  1.0
  O  O35  1  0.500  0.000  0.232  1.0
  O  O36  1  0.500  0.500  0.503  1.0
  O  O37  1  0.500  0.500  0.999  1.0
  O  O38  1  0.713  0.576  0.233  1.0
  O  O39  1  0.212  0.923  0.763  1.0
  O  O40  1  0.000  0.000  0.503  1.0
  O  O41  1  0.712  0.577  0.763  1.0
  O  O42  1  0.000  0.000  0.999  1.0
  O  O43  1  0.577  0.288  0.763  1.0
[/CIF]
.
The compound described by KNbSi2O7 crystallizes in the tetragonal P4bm space group. K(1) is bonded in a 12-coordinate geometry to one O(4), one O(5), two equivalent O(7), four equivalent O(1), and four equivalent O(2) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(6), one O(7), and four equivalent O(1) atoms to form distorted NbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedra are not tilted. In the second Nb site, Nb(2) is bonded to one O(6), one O(7), and four equivalent O(2) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedra are not tilted. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 31°. In the second Si site, Si(2) is bonded to one O(3), one O(5), and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Nb(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 18°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the second O site, O(7) is bonded in a distorted linear geometry to four equivalent K(1), one Nb(1), and one Nb(2) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), one Nb(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to two equivalent K(1), one Nb(2), and one Si(2) atom. In the fifth O site, O(3) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(1) atoms. In the seventh O site, O(5) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1) and two equivalent Si(2) atoms. is represented by the CIF file [CIF]
data_KNbSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.877
_cell_length_b   8.877
_cell_length_c   8.274
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   652.088
_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
  K  K0  1  0.178  0.678  0.992  1.0
  K  K1  1  0.678  0.822  0.992  1.0
  K  K2  1  0.822  0.322  0.992  1.0
  K  K3  1  0.322  0.178  0.992  1.0
  Nb  Nb4  1  0.500  0.500  0.720  1.0
  Nb  Nb5  1  0.500  0.500  0.218  1.0
  Nb  Nb6  1  0.000  0.000  0.720  1.0
  Nb  Nb7  1  0.000  0.000  0.218  1.0
  Si  Si8  1  0.124  0.376  0.693  1.0
  Si  Si9  1  0.877  0.623  0.303  1.0
  Si  Si10  1  0.377  0.877  0.303  1.0
  Si  Si11  1  0.623  0.123  0.303  1.0
  Si  Si12  1  0.624  0.124  0.693  1.0
  Si  Si13  1  0.376  0.876  0.693  1.0
  Si  Si14  1  0.876  0.624  0.693  1.0
  Si  Si15  1  0.123  0.377  0.303  1.0
  O  O16  1  0.423  0.712  0.763  1.0
  O  O17  1  0.924  0.787  0.233  1.0
  O  O18  1  0.077  0.212  0.763  1.0
  O  O19  1  0.288  0.423  0.763  1.0
  O  O20  1  0.576  0.287  0.233  1.0
  O  O21  1  0.788  0.077  0.763  1.0
  O  O22  1  0.287  0.424  0.233  1.0
  O  O23  1  0.620  0.120  0.498  1.0
  O  O24  1  0.787  0.076  0.233  1.0
  O  O25  1  0.120  0.380  0.498  1.0
  O  O26  1  0.000  0.500  0.764  1.0
  O  O27  1  0.000  0.500  0.232  1.0
  O  O28  1  0.380  0.880  0.498  1.0
  O  O29  1  0.500  0.000  0.764  1.0
  O  O30  1  0.880  0.620  0.498  1.0
  O  O31  1  0.923  0.788  0.763  1.0
  O  O32  1  0.076  0.213  0.233  1.0
  O  O33  1  0.424  0.713  0.233  1.0
  O  O34  1  0.213  0.924  0.233  1.0
  O  O35  1  0.500  0.000  0.232  1.0
  O  O36  1  0.500  0.500  0.503  1.0
  O  O37  1  0.500  0.500  0.999  1.0
  O  O38  1  0.713  0.576  0.233  1.0
  O  O39  1  0.212  0.923  0.763  1.0
  O  O40  1  0.000  0.000  0.503  1.0
  O  O41  1  0.712  0.577  0.763  1.0
  O  O42  1  0.000  0.000  0.999  1.0
  O  O43  1  0.577  0.288  0.763  1.0
[/CIF]
.