data_global _chemical_name_mineral 'Tridymite' loop_ _publ_author_name 'Kihara K' 'Matsumoto T' 'Imamura M' _journal_name_full 'Zeitschrift fur Kristallographie' _journal_volume 177 _journal_year 1986 _journal_page_first 27 _journal_page_last 38 _publ_section_title ; Structural change of orthorhombic-I tridymite with temperature: A study based on second-order thermal-vibrational parameters Note: Dollase's model, T = 493 K ; _database_code_amcsd 0020932 _chemical_compound_source 'synthetic refractory silica brick' _chemical_formula_sum 'Si O2' _cell_length_a 8.756 _cell_length_b 5.024 _cell_length_c 8.213 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 361.291 _exptl_crystal_density_diffrn 2.209 _symmetry_space_group_name_H-M 'C 2 2 21' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2+x,1/2+y,z' '-x,y,-z' '1/2-x,1/2+y,-z' 'x,-y,1/2-z' '1/2+x,1/2-y,1/2-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 Si 0.16810 0.54700 0.43790 O1 0.33150 0.00000 0.75000 O2 0.00000 0.57140 0.50000 O3 0.25350 0.31760 0.52920 loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_12 _atom_site_aniso_U_13 _atom_site_aniso_U_23 Si 0.03690 0.04437 0.03622 0.00223 0.00146 -0.00523 O1 0.11147 0.11905 0.03827 0.00000 0.00000 0.01463 O2 0.04156 0.17774 0.12165 0.00000 -0.00146 0.00000 O3 0.14216 0.08056 0.08953 0.05661 -0.01639 0.01902