SiO2 Boisen M B, Gibbs G V, Bukowinski M S T Physics and Chemistry of Minerals 21 (1994) 269-284 Framework silica structures generated using simulated annealing with a potential energy function based on an H6Si2O7 molecule Sample: 19 _database_code_amcsd 0007884 4.7082 5.5282 5.0064 90 107.8346 90 Pm atom x y z Si1 0 .5 0 Si2 .53662 .5 .53762 Si3 .95079 0 .21653 Si4 .54481 0 .55830 O1 .30313 0 .25680 O2 .46696 .74682 .68687 O3 .90747 .5 .65132 O4 .82996 .25443 .05792 O5 .87559 0 .51469 O6 .35985 .5 .19218