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 = 443 K ; _database_code_amcsd 0020931 _chemical_compound_source 'synthetic refractory silica brick' _chemical_formula_sum 'Si O2' _cell_length_a 8.730 _cell_length_b 5.000 _cell_length_c 8.201 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 357.974 _exptl_crystal_density_diffrn 2.230 _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 0.16850 0.55120 0.43800 O1 0.32720 0.00000 0.75000 O2 0.00000 0.57740 0.50000 O3 0.25030 0.31820 0.53010 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 0.02934 0.04534 0.03714 0.00177 0.00472 -0.00436 O1 0.09575 0.13248 0.03782 0.00000 0.00000 0.01724 O2 0.03243 0.16946 0.11176 0.00000 -0.01959 0.00000 O3 0.13320 0.10727 0.08723 0.06037 0.00254 0.01184