The compound described by SiO2 is Keatite-like structured and crystallizes in the orthorhombic Cmcm space group. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom 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(5) atoms to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(4), one O(8), 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 two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the seventh O site, O(7) is bonded in a linear geometry to two equivalent Si(2) atoms. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to two equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_SiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.505
_cell_length_b   10.154
_cell_length_c   14.013
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   111.689
_symmetry_Int_Tables_number   1
_cell_volume   992.336
_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  0.882  0.352  0.950  1.0
  Si  Si1  1  0.921  0.841  0.540  1.0
  Si  Si2  1  0.118  0.648  0.450  1.0
  Si  Si3  1  0.530  0.648  0.450  1.0
  Si  Si4  1  0.860  0.720  0.750  1.0
  Si  Si5  1  0.470  0.352  0.550  1.0
  Si  Si6  1  0.118  0.648  0.050  1.0
  Si  Si7  1  0.140  0.280  0.250  1.0
  Si  Si8  1  0.557  0.526  0.250  1.0
  Si  Si9  1  0.470  0.352  0.950  1.0
  Si  Si10  1  0.443  0.474  0.750  1.0
  Si  Si11  1  0.530  0.648  0.050  1.0
  Si  Si12  1  0.031  0.474  0.750  1.0
  Si  Si13  1  0.079  0.159  0.040  1.0
  Si  Si14  1  0.079  0.159  0.460  1.0
  Si  Si15  1  0.921  0.841  0.960  1.0
  Si  Si16  1  0.882  0.352  0.550  1.0
  Si  Si17  1  0.969  0.526  0.250  1.0
  O  O18  1  0.344  0.689  0.037  1.0
  O  O19  1  0.656  0.311  0.537  1.0
  O  O20  1  0.500  0.500  0.500  1.0
  O  O21  1  0.940  0.372  0.839  1.0
  O  O22  1  0.018  0.383  0.250  1.0
  O  O23  1  0.293  0.231  0.502  1.0
  O  O24  1  0.911  0.821  0.656  1.0
  O  O25  1  0.940  0.372  0.661  1.0
  O  O26  1  0.911  0.821  0.844  1.0
  O  O27  1  0.937  0.231  0.998  1.0
  O  O28  1  0.000  0.000  0.000  1.0
  O  O29  1  0.365  0.383  0.250  1.0
  O  O30  1  0.063  0.769  0.002  1.0
  O  O31  1  0.707  0.769  0.002  1.0
  O  O32  1  0.432  0.372  0.661  1.0
  O  O33  1  0.089  0.179  0.156  1.0
  O  O34  1  0.937  0.231  0.502  1.0
  O  O35  1  0.738  0.476  0.250  1.0
  O  O36  1  0.089  0.179  0.344  1.0
  O  O37  1  0.262  0.524  0.750  1.0
  O  O38  1  0.568  0.628  0.339  1.0
  O  O39  1  0.344  0.689  0.463  1.0
  O  O40  1  0.000  0.500  0.000  1.0
  O  O41  1  0.432  0.372  0.839  1.0
  O  O42  1  0.707  0.769  0.498  1.0
  O  O43  1  0.568  0.628  0.161  1.0
  O  O44  1  0.063  0.769  0.498  1.0
  O  O45  1  0.656  0.311  0.963  1.0
  O  O46  1  0.000  0.000  0.500  1.0
  O  O47  1  0.982  0.617  0.750  1.0
  O  O48  1  0.060  0.628  0.339  1.0
  O  O49  1  0.060  0.628  0.161  1.0
  O  O50  1  0.635  0.617  0.750  1.0
  O  O51  1  0.500  0.500  0.000  1.0
  O  O52  1  0.293  0.231  0.998  1.0
  O  O53  1  0.000  0.500  0.500  1.0
[/CIF]
.
The compound described by SiO2 is Keatite-like structured and crystallizes in the orthorhombic Cmcm space group. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom 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(5) atoms to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(4), one O(8), 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 two equivalent Si(1) atoms. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the seventh O site, O(7) is bonded in a linear geometry to two equivalent Si(2) atoms. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to two equivalent Si(4) atoms. is represented by the CIF file [CIF]
data_SiO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.505
_cell_length_b   10.154
_cell_length_c   14.013
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   111.689
_symmetry_Int_Tables_number   1
_cell_volume   992.336
_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  0.882  0.352  0.950  1.0
  Si  Si1  1  0.921  0.841  0.540  1.0
  Si  Si2  1  0.118  0.648  0.450  1.0
  Si  Si3  1  0.530  0.648  0.450  1.0
  Si  Si4  1  0.860  0.720  0.750  1.0
  Si  Si5  1  0.470  0.352  0.550  1.0
  Si  Si6  1  0.118  0.648  0.050  1.0
  Si  Si7  1  0.140  0.280  0.250  1.0
  Si  Si8  1  0.557  0.526  0.250  1.0
  Si  Si9  1  0.470  0.352  0.950  1.0
  Si  Si10  1  0.443  0.474  0.750  1.0
  Si  Si11  1  0.530  0.648  0.050  1.0
  Si  Si12  1  0.031  0.474  0.750  1.0
  Si  Si13  1  0.079  0.159  0.040  1.0
  Si  Si14  1  0.079  0.159  0.460  1.0
  Si  Si15  1  0.921  0.841  0.960  1.0
  Si  Si16  1  0.882  0.352  0.550  1.0
  Si  Si17  1  0.969  0.526  0.250  1.0
  O  O18  1  0.344  0.689  0.037  1.0
  O  O19  1  0.656  0.311  0.537  1.0
  O  O20  1  0.500  0.500  0.500  1.0
  O  O21  1  0.940  0.372  0.839  1.0
  O  O22  1  0.018  0.383  0.250  1.0
  O  O23  1  0.293  0.231  0.502  1.0
  O  O24  1  0.911  0.821  0.656  1.0
  O  O25  1  0.940  0.372  0.661  1.0
  O  O26  1  0.911  0.821  0.844  1.0
  O  O27  1  0.937  0.231  0.998  1.0
  O  O28  1  0.000  0.000  0.000  1.0
  O  O29  1  0.365  0.383  0.250  1.0
  O  O30  1  0.063  0.769  0.002  1.0
  O  O31  1  0.707  0.769  0.002  1.0
  O  O32  1  0.432  0.372  0.661  1.0
  O  O33  1  0.089  0.179  0.156  1.0
  O  O34  1  0.937  0.231  0.502  1.0
  O  O35  1  0.738  0.476  0.250  1.0
  O  O36  1  0.089  0.179  0.344  1.0
  O  O37  1  0.262  0.524  0.750  1.0
  O  O38  1  0.568  0.628  0.339  1.0
  O  O39  1  0.344  0.689  0.463  1.0
  O  O40  1  0.000  0.500  0.000  1.0
  O  O41  1  0.432  0.372  0.839  1.0
  O  O42  1  0.707  0.769  0.498  1.0
  O  O43  1  0.568  0.628  0.161  1.0
  O  O44  1  0.063  0.769  0.498  1.0
  O  O45  1  0.656  0.311  0.963  1.0
  O  O46  1  0.000  0.000  0.500  1.0
  O  O47  1  0.982  0.617  0.750  1.0
  O  O48  1  0.060  0.628  0.339  1.0
  O  O49  1  0.060  0.628  0.161  1.0
  O  O50  1  0.635  0.617  0.750  1.0
  O  O51  1  0.500  0.500  0.000  1.0
  O  O52  1  0.293  0.231  0.998  1.0
  O  O53  1  0.000  0.500  0.500  1.0
[/CIF]
.