The material described by SiO2 is Low Tridymite-like structured and crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(5), one O(7), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(1), one O(2), one O(4), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(8) is bonded in a linear geometry to two equivalent Si(3) atoms. In the second O site, O(9) is bonded in a linear geometry to two equivalent Si(2) atoms. In the third O site, O(1) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the ninth O site, O(7) 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   7.880
_cell_length_b   8.827
_cell_length_c   8.826
_cell_angle_alpha   90.302
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   613.831
_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  0.126  0.161  0.354  1.0
  Si  Si1  1  0.630  0.104  0.595  1.0
  Si  Si2  1  0.143  0.595  0.090  1.0
  Si  Si3  1  0.870  0.104  0.095  1.0
  Si  Si4  1  0.874  0.839  0.646  1.0
  Si  Si5  1  0.643  0.405  0.410  1.0
  Si  Si6  1  0.857  0.405  0.910  1.0
  Si  Si7  1  0.605  0.658  0.842  1.0
  Si  Si8  1  0.370  0.896  0.405  1.0
  Si  Si9  1  0.130  0.896  0.905  1.0
  Si  Si10  1  0.395  0.342  0.158  1.0
  Si  Si11  1  0.357  0.595  0.590  1.0
  Si  Si12  1  0.895  0.658  0.342  1.0
  Si  Si13  1  0.374  0.161  0.854  1.0
  Si  Si14  1  0.626  0.839  0.146  1.0
  Si  Si15  1  0.105  0.342  0.658  1.0
  O  O16  1  0.818  0.499  0.401  1.0
  O  O17  1  0.179  0.751  0.004  1.0
  O  O18  1  0.682  0.499  0.901  1.0
  O  O19  1  0.267  0.271  0.281  1.0
  O  O20  1  0.424  0.628  0.760  1.0
  O  O21  1  0.767  0.729  0.219  1.0
  O  O22  1  0.701  0.009  0.133  1.0
  O  O23  1  0.580  0.775  0.980  1.0
  O  O24  1  0.201  0.991  0.367  1.0
  O  O25  1  0.799  0.009  0.633  1.0
  O  O26  1  0.233  0.271  0.781  1.0
  O  O27  1  0.957  0.157  0.252  1.0
  O  O28  1  0.043  0.843  0.748  1.0
  O  O29  1  0.543  0.157  0.752  1.0
  O  O30  1  0.318  0.501  0.099  1.0
  O  O31  1  0.321  0.751  0.504  1.0
  O  O32  1  0.821  0.249  0.996  1.0
  O  O33  1  0.182  0.501  0.599  1.0
  O  O34  1  0.733  0.729  0.719  1.0
  O  O35  1  0.299  0.991  0.867  1.0
  O  O36  1  0.080  0.225  0.520  1.0
  O  O37  1  0.500  0.500  0.500  1.0
  O  O38  1  0.576  0.372  0.240  1.0
  O  O39  1  0.076  0.628  0.260  1.0
  O  O40  1  0.457  0.843  0.248  1.0
  O  O41  1  0.679  0.249  0.496  1.0
  O  O42  1  0.420  0.225  0.020  1.0
  O  O43  1  0.924  0.372  0.740  1.0
  O  O44  1  0.000  0.500  0.000  1.0
  O  O45  1  0.000  0.000  0.000  1.0
  O  O46  1  0.920  0.775  0.480  1.0
  O  O47  1  0.500  0.000  0.500  1.0
[/CIF]
.
The material described by SiO2 is Low Tridymite-like structured and crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(5), one O(7), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(1), one O(2), one O(4), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(8) is bonded in a linear geometry to two equivalent Si(3) atoms. In the second O site, O(9) is bonded in a linear geometry to two equivalent Si(2) atoms. In the third O site, O(1) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the ninth O site, O(7) 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   7.880
_cell_length_b   8.827
_cell_length_c   8.826
_cell_angle_alpha   90.302
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   613.831
_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  0.126  0.161  0.354  1.0
  Si  Si1  1  0.630  0.104  0.595  1.0
  Si  Si2  1  0.143  0.595  0.090  1.0
  Si  Si3  1  0.870  0.104  0.095  1.0
  Si  Si4  1  0.874  0.839  0.646  1.0
  Si  Si5  1  0.643  0.405  0.410  1.0
  Si  Si6  1  0.857  0.405  0.910  1.0
  Si  Si7  1  0.605  0.658  0.842  1.0
  Si  Si8  1  0.370  0.896  0.405  1.0
  Si  Si9  1  0.130  0.896  0.905  1.0
  Si  Si10  1  0.395  0.342  0.158  1.0
  Si  Si11  1  0.357  0.595  0.590  1.0
  Si  Si12  1  0.895  0.658  0.342  1.0
  Si  Si13  1  0.374  0.161  0.854  1.0
  Si  Si14  1  0.626  0.839  0.146  1.0
  Si  Si15  1  0.105  0.342  0.658  1.0
  O  O16  1  0.818  0.499  0.401  1.0
  O  O17  1  0.179  0.751  0.004  1.0
  O  O18  1  0.682  0.499  0.901  1.0
  O  O19  1  0.267  0.271  0.281  1.0
  O  O20  1  0.424  0.628  0.760  1.0
  O  O21  1  0.767  0.729  0.219  1.0
  O  O22  1  0.701  0.009  0.133  1.0
  O  O23  1  0.580  0.775  0.980  1.0
  O  O24  1  0.201  0.991  0.367  1.0
  O  O25  1  0.799  0.009  0.633  1.0
  O  O26  1  0.233  0.271  0.781  1.0
  O  O27  1  0.957  0.157  0.252  1.0
  O  O28  1  0.043  0.843  0.748  1.0
  O  O29  1  0.543  0.157  0.752  1.0
  O  O30  1  0.318  0.501  0.099  1.0
  O  O31  1  0.321  0.751  0.504  1.0
  O  O32  1  0.821  0.249  0.996  1.0
  O  O33  1  0.182  0.501  0.599  1.0
  O  O34  1  0.733  0.729  0.719  1.0
  O  O35  1  0.299  0.991  0.867  1.0
  O  O36  1  0.080  0.225  0.520  1.0
  O  O37  1  0.500  0.500  0.500  1.0
  O  O38  1  0.576  0.372  0.240  1.0
  O  O39  1  0.076  0.628  0.260  1.0
  O  O40  1  0.457  0.843  0.248  1.0
  O  O41  1  0.679  0.249  0.496  1.0
  O  O42  1  0.420  0.225  0.020  1.0
  O  O43  1  0.924  0.372  0.740  1.0
  O  O44  1  0.000  0.500  0.000  1.0
  O  O45  1  0.000  0.000  0.000  1.0
  O  O46  1  0.920  0.775  0.480  1.0
  O  O47  1  0.500  0.000  0.500  1.0
[/CIF]
.