The material described by SiO2 is High (Orthorhombic) Tridymite-like structured and crystallizes in the orthorhombic Imma space group. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(6), one O(7), and two equivalent O(8) atoms to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(2), one O(5), and two equivalent O(8) atoms to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to two equivalent O(3) and two equivalent O(7) atoms to form corner-sharing SiO4 tetrahedra. In the fifth Si site, Si(5) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form corner-sharing SiO4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a linear geometry to one Si(3) and one Si(5) atom. In the third O site, O(3) is bonded in a linear geometry to one Si(4) and one Si(5) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the sixth O site, O(6) is bonded in a linear geometry to two equivalent Si(2) atoms. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Si(2) and one Si(3) atom. is represented by the CIF card [CIF]
data_SiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.973
_cell_length_b   14.973
_cell_length_c   14.973
_cell_angle_alpha   159.811
_cell_angle_beta   124.290
_cell_angle_gamma   59.872
_symmetry_Int_Tables_number   1
_cell_volume   952.975
_cell_formula_units_Z   16
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  0.923  0.784  0.139  1.0
  Si  Si1  1  0.856  0.216  0.639  1.0
  Si  Si2  1  0.077  0.216  0.861  1.0
  Si  Si3  1  0.144  0.784  0.361  1.0
  Si  Si4  1  0.902  0.441  0.460  1.0
  Si  Si5  1  0.519  0.559  0.960  1.0
  Si  Si6  1  0.098  0.559  0.540  1.0
  Si  Si7  1  0.481  0.441  0.040  1.0
  Si  Si8  1  0.948  0.894  0.054  1.0
  Si  Si9  1  0.660  0.106  0.554  1.0
  Si  Si10  1  0.052  0.106  0.946  1.0
  Si  Si11  1  0.340  0.894  0.446  1.0
  Si  Si12  1  0.276  0.526  0.750  1.0
  Si  Si13  1  0.724  0.474  0.250  1.0
  Si  Si14  1  0.205  0.955  0.250  1.0
  Si  Si15  1  0.795  0.045  0.750  1.0
  O  O16  1  0.053  0.803  0.250  1.0
  O  O17  1  0.947  0.197  0.750  1.0
  O  O18  1  0.077  0.920  0.157  1.0
  O  O19  1  0.738  0.080  0.657  1.0
  O  O20  1  0.923  0.080  0.843  1.0
  O  O21  1  0.262  0.920  0.343  1.0
  O  O22  1  0.240  0.241  0.500  1.0
  O  O23  1  0.760  0.759  0.500  1.0
  O  O24  1  0.760  0.260  0.000  1.0
  O  O25  1  0.240  0.740  1.000  1.0
  O  O26  1  0.869  0.500  0.869  1.0
  O  O27  1  0.131  0.000  0.631  1.0
  O  O28  1  0.131  0.500  0.131  1.0
  O  O29  1  0.869  0.000  0.369  1.0
  O  O30  1  0.900  0.832  0.068  1.0
  O  O31  1  0.736  0.168  0.568  1.0
  O  O32  1  0.100  0.168  0.932  1.0
  O  O33  1  0.264  0.832  0.432  1.0
  O  O34  1  0.000  0.500  0.500  1.0
  O  O35  1  0.500  0.500  0.000  1.0
  O  O36  1  0.215  0.561  0.655  1.0
  O  O37  1  0.594  0.439  0.155  1.0
  O  O38  1  0.785  0.439  0.345  1.0
  O  O39  1  0.406  0.561  0.845  1.0
  O  O40  1  0.908  0.161  0.246  1.0
  O  O41  1  0.585  0.839  0.247  1.0
  O  O42  1  0.092  0.338  0.253  1.0
  O  O43  1  0.415  0.662  0.254  1.0
  O  O44  1  0.092  0.839  0.754  1.0
  O  O45  1  0.415  0.161  0.753  1.0
  O  O46  1  0.908  0.662  0.747  1.0
  O  O47  1  0.585  0.338  0.746  1.0
[/CIF]
.
The material described by SiO2 is High (Orthorhombic) Tridymite-like structured and crystallizes in the orthorhombic Imma space group. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(6), one O(7), and two equivalent O(8) atoms to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(2), one O(5), and two equivalent O(8) atoms to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to two equivalent O(3) and two equivalent O(7) atoms to form corner-sharing SiO4 tetrahedra. In the fifth Si site, Si(5) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form corner-sharing SiO4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a linear geometry to one Si(3) and one Si(5) atom. In the third O site, O(3) is bonded in a linear geometry to one Si(4) and one Si(5) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the sixth O site, O(6) is bonded in a linear geometry to two equivalent Si(2) atoms. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Si(2) and one Si(3) atom. is represented by the CIF card [CIF]
data_SiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   14.973
_cell_length_b   14.973
_cell_length_c   14.973
_cell_angle_alpha   159.811
_cell_angle_beta   124.290
_cell_angle_gamma   59.872
_symmetry_Int_Tables_number   1
_cell_volume   952.975
_cell_formula_units_Z   16
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  0.923  0.784  0.139  1.0
  Si  Si1  1  0.856  0.216  0.639  1.0
  Si  Si2  1  0.077  0.216  0.861  1.0
  Si  Si3  1  0.144  0.784  0.361  1.0
  Si  Si4  1  0.902  0.441  0.460  1.0
  Si  Si5  1  0.519  0.559  0.960  1.0
  Si  Si6  1  0.098  0.559  0.540  1.0
  Si  Si7  1  0.481  0.441  0.040  1.0
  Si  Si8  1  0.948  0.894  0.054  1.0
  Si  Si9  1  0.660  0.106  0.554  1.0
  Si  Si10  1  0.052  0.106  0.946  1.0
  Si  Si11  1  0.340  0.894  0.446  1.0
  Si  Si12  1  0.276  0.526  0.750  1.0
  Si  Si13  1  0.724  0.474  0.250  1.0
  Si  Si14  1  0.205  0.955  0.250  1.0
  Si  Si15  1  0.795  0.045  0.750  1.0
  O  O16  1  0.053  0.803  0.250  1.0
  O  O17  1  0.947  0.197  0.750  1.0
  O  O18  1  0.077  0.920  0.157  1.0
  O  O19  1  0.738  0.080  0.657  1.0
  O  O20  1  0.923  0.080  0.843  1.0
  O  O21  1  0.262  0.920  0.343  1.0
  O  O22  1  0.240  0.241  0.500  1.0
  O  O23  1  0.760  0.759  0.500  1.0
  O  O24  1  0.760  0.260  0.000  1.0
  O  O25  1  0.240  0.740  1.000  1.0
  O  O26  1  0.869  0.500  0.869  1.0
  O  O27  1  0.131  0.000  0.631  1.0
  O  O28  1  0.131  0.500  0.131  1.0
  O  O29  1  0.869  0.000  0.369  1.0
  O  O30  1  0.900  0.832  0.068  1.0
  O  O31  1  0.736  0.168  0.568  1.0
  O  O32  1  0.100  0.168  0.932  1.0
  O  O33  1  0.264  0.832  0.432  1.0
  O  O34  1  0.000  0.500  0.500  1.0
  O  O35  1  0.500  0.500  0.000  1.0
  O  O36  1  0.215  0.561  0.655  1.0
  O  O37  1  0.594  0.439  0.155  1.0
  O  O38  1  0.785  0.439  0.345  1.0
  O  O39  1  0.406  0.561  0.845  1.0
  O  O40  1  0.908  0.161  0.246  1.0
  O  O41  1  0.585  0.839  0.247  1.0
  O  O42  1  0.092  0.338  0.253  1.0
  O  O43  1  0.415  0.662  0.254  1.0
  O  O44  1  0.092  0.839  0.754  1.0
  O  O45  1  0.415  0.161  0.753  1.0
  O  O46  1  0.908  0.662  0.747  1.0
  O  O47  1  0.585  0.338  0.746  1.0
[/CIF]
.