data_global _amcsd_formula_title 'SiO2' loop_ _publ_author_name 'Boisen M B' 'Gibbs G V' 'Bukowinski M S T' _journal_name_full 'Physics and Chemistry of Minerals' _journal_volume 21 _journal_year 1994 _journal_page_first 269 _journal_page_last 284 _publ_section_title ; Framework silica structures generated using simulated annealing with a potential energy function based on an H6Si2O7 molecule Sample: 16 ; _database_code_amcsd 0007881 _chemical_formula_sum 'Si O2' _cell_length_a 6.6395 _cell_length_b 8.0488 _cell_length_c 5.4184 _cell_angle_alpha 90 _cell_angle_beta 99.9967 _cell_angle_gamma 90 _cell_volume 285.163 _exptl_crystal_density_diffrn 2.799 _symmetry_space_group_name_H-M 'C 1 c 1' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2+x,1/2+y,z' 'x,-y,1/2+z' '1/2+x,1/2-y,1/2+z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z Si1 0.00000 0.03951 0.50000 Si2 0.04928 0.41410 0.41569 O1 0.29789 0.58048 0.97139 O2 0.12542 0.01394 0.78199 O3 0.47304 0.96257 0.11972 O4 0.44951 0.73454 0.46074