data_global _chemical_name_mineral 'Tridymite' loop_ _publ_author_name 'Graetsch H' 'Topalovic-Dierdorf I' _journal_name_full 'European Journal of Mineralogy' _journal_volume 8 _journal_year 1996 _journal_page_first 103 _journal_page_last 113 _publ_section_title ; 29Si MAS NMR spectrum and superstructure of modulated tridymite L3-To(MX-1) Sample: average crystal structure ; _database_code_amcsd 0006616 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'Si O2' _cell_length_a 5.007 _cell_length_b 8.6004 _cell_length_c 8.2169 _cell_angle_alpha 90 _cell_angle_beta 91.512 _cell_angle_gamma 90 _cell_volume 353.715 _exptl_crystal_density_diffrn 2.257 _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 _atom_site_U_iso_or_equiv Si1 0.07640 0.30730 0.21080 0.05200 Si2 0.07730 0.35920 0.83520 0.05200 O1 0.28850 0.75300 0.25340 0.04400 O2 0.14400 0.46470 0.30820 0.08500 O3 0.28840 0.17970 0.27030 0.13800 O4 0.58260 0.16680 0.51980 0.18800 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 Si1 0.04300 0.03300 0.08000 0.00400 0.03100 0.00600 Si2 0.04200 0.03400 0.08200 0.00400 0.03100 0.00800 O1 0.03900 0.04700 0.04600 0.01000 0.00100 -0.00300 O2 0.04800 0.03000 0.17600 -0.01400 -0.01700 0.00900 O3 0.03200 0.03200 0.35000 0.00800 -0.00200 0.00800 O4 0.26600 0.21600 0.09000 -0.02300 0.13200 -0.01400