The structure described by SiO2 is Low Tridymite-like structured and crystallizes in the tetragonal P4_2/mmc space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to four equivalent O(5) atoms to form corner-sharing SiO4 tetrahedra. There are five inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Si(2) atoms. In the third O site, O(5) is bonded in a bent 120 degrees geometry to one Si(2) and one Si(3) atom. In the fourth O site, O(1) is bonded in a linear geometry to two equivalent Si(1) atoms. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the CIF file [CIF]
data_SiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.174
_cell_length_b   7.174
_cell_length_c   20.875
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   1074.277
_cell_formula_units_Z   18
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
  Si  Si0  1  0.284  0.500  0.077  1.0
  Si  Si1  1  0.500  0.284  0.577  1.0
  Si  Si2  1  0.500  0.716  0.577  1.0
  Si  Si3  1  0.284  0.500  0.923  1.0
  Si  Si4  1  0.716  0.500  0.923  1.0
  Si  Si5  1  0.716  0.500  0.077  1.0
  Si  Si6  1  0.500  0.284  0.423  1.0
  Si  Si7  1  0.500  0.716  0.423  1.0
  Si  Si8  1  0.000  0.794  0.127  1.0
  Si  Si9  1  0.206  0.000  0.627  1.0
  Si  Si10  1  0.794  0.000  0.627  1.0
  Si  Si11  1  0.000  0.206  0.873  1.0
  Si  Si12  1  0.000  0.794  0.873  1.0
  Si  Si13  1  0.000  0.206  0.127  1.0
  Si  Si14  1  0.794  0.000  0.373  1.0
  Si  Si15  1  0.206  0.000  0.373  1.0
  Si  Si16  1  0.000  0.000  0.750  1.0
  Si  Si17  1  0.000  0.000  0.250  1.0
  O  O18  1  0.266  0.500  0.000  1.0
  O  O19  1  0.500  0.266  0.500  1.0
  O  O20  1  0.500  0.734  0.500  1.0
  O  O21  1  0.734  0.500  0.000  1.0
  O  O22  1  0.185  0.684  0.105  1.0
  O  O23  1  0.316  0.185  0.605  1.0
  O  O24  1  0.684  0.815  0.605  1.0
  O  O25  1  0.185  0.316  0.895  1.0
  O  O26  1  0.815  0.684  0.895  1.0
  O  O27  1  0.815  0.316  0.105  1.0
  O  O28  1  0.684  0.185  0.395  1.0
  O  O29  1  0.316  0.815  0.395  1.0
  O  O30  1  0.815  0.316  0.895  1.0
  O  O31  1  0.684  0.815  0.395  1.0
  O  O32  1  0.316  0.185  0.395  1.0
  O  O33  1  0.815  0.684  0.105  1.0
  O  O34  1  0.185  0.316  0.105  1.0
  O  O35  1  0.185  0.684  0.895  1.0
  O  O36  1  0.316  0.815  0.605  1.0
  O  O37  1  0.684  0.185  0.605  1.0
  O  O38  1  0.500  0.500  0.097  1.0
  O  O39  1  0.500  0.500  0.597  1.0
  O  O40  1  0.500  0.500  0.903  1.0
  O  O41  1  0.500  0.500  0.403  1.0
  O  O42  1  0.000  0.000  0.095  1.0
  O  O43  1  0.000  0.000  0.595  1.0
  O  O44  1  0.000  0.000  0.905  1.0
  O  O45  1  0.000  0.000  0.405  1.0
  O  O46  1  0.000  0.818  0.204  1.0
  O  O47  1  0.182  0.000  0.704  1.0
  O  O48  1  0.818  0.000  0.704  1.0
  O  O49  1  0.000  0.182  0.796  1.0
  O  O50  1  0.000  0.818  0.796  1.0
  O  O51  1  0.000  0.182  0.204  1.0
  O  O52  1  0.818  0.000  0.296  1.0
  O  O53  1  0.182  0.000  0.296  1.0
[/CIF]
.
The structure described by SiO2 is Low Tridymite-like structured and crystallizes in the tetragonal P4_2/mmc space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to four equivalent O(5) atoms to form corner-sharing SiO4 tetrahedra. There are five inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Si(2) atoms. In the third O site, O(5) is bonded in a bent 120 degrees geometry to one Si(2) and one Si(3) atom. In the fourth O site, O(1) is bonded in a linear geometry to two equivalent Si(1) atoms. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the CIF file [CIF]
data_SiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.174
_cell_length_b   7.174
_cell_length_c   20.875
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   1074.277
_cell_formula_units_Z   18
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
  Si  Si0  1  0.284  0.500  0.077  1.0
  Si  Si1  1  0.500  0.284  0.577  1.0
  Si  Si2  1  0.500  0.716  0.577  1.0
  Si  Si3  1  0.284  0.500  0.923  1.0
  Si  Si4  1  0.716  0.500  0.923  1.0
  Si  Si5  1  0.716  0.500  0.077  1.0
  Si  Si6  1  0.500  0.284  0.423  1.0
  Si  Si7  1  0.500  0.716  0.423  1.0
  Si  Si8  1  0.000  0.794  0.127  1.0
  Si  Si9  1  0.206  0.000  0.627  1.0
  Si  Si10  1  0.794  0.000  0.627  1.0
  Si  Si11  1  0.000  0.206  0.873  1.0
  Si  Si12  1  0.000  0.794  0.873  1.0
  Si  Si13  1  0.000  0.206  0.127  1.0
  Si  Si14  1  0.794  0.000  0.373  1.0
  Si  Si15  1  0.206  0.000  0.373  1.0
  Si  Si16  1  0.000  0.000  0.750  1.0
  Si  Si17  1  0.000  0.000  0.250  1.0
  O  O18  1  0.266  0.500  0.000  1.0
  O  O19  1  0.500  0.266  0.500  1.0
  O  O20  1  0.500  0.734  0.500  1.0
  O  O21  1  0.734  0.500  0.000  1.0
  O  O22  1  0.185  0.684  0.105  1.0
  O  O23  1  0.316  0.185  0.605  1.0
  O  O24  1  0.684  0.815  0.605  1.0
  O  O25  1  0.185  0.316  0.895  1.0
  O  O26  1  0.815  0.684  0.895  1.0
  O  O27  1  0.815  0.316  0.105  1.0
  O  O28  1  0.684  0.185  0.395  1.0
  O  O29  1  0.316  0.815  0.395  1.0
  O  O30  1  0.815  0.316  0.895  1.0
  O  O31  1  0.684  0.815  0.395  1.0
  O  O32  1  0.316  0.185  0.395  1.0
  O  O33  1  0.815  0.684  0.105  1.0
  O  O34  1  0.185  0.316  0.105  1.0
  O  O35  1  0.185  0.684  0.895  1.0
  O  O36  1  0.316  0.815  0.605  1.0
  O  O37  1  0.684  0.185  0.605  1.0
  O  O38  1  0.500  0.500  0.097  1.0
  O  O39  1  0.500  0.500  0.597  1.0
  O  O40  1  0.500  0.500  0.903  1.0
  O  O41  1  0.500  0.500  0.403  1.0
  O  O42  1  0.000  0.000  0.095  1.0
  O  O43  1  0.000  0.000  0.595  1.0
  O  O44  1  0.000  0.000  0.905  1.0
  O  O45  1  0.000  0.000  0.405  1.0
  O  O46  1  0.000  0.818  0.204  1.0
  O  O47  1  0.182  0.000  0.704  1.0
  O  O48  1  0.818  0.000  0.704  1.0
  O  O49  1  0.000  0.182  0.796  1.0
  O  O50  1  0.000  0.818  0.796  1.0
  O  O51  1  0.000  0.182  0.204  1.0
  O  O52  1  0.818  0.000  0.296  1.0
  O  O53  1  0.182  0.000  0.296  1.0
[/CIF]
.