data_global
_chemical_name_mineral 'Tridymite'
loop_
_publ_author_name
'Graetsch H'
_journal_name_full 'Physics and Chemistry of Minerals'
_journal_volume 28 
_journal_year 2001
_journal_page_first 313
_journal_page_last 321
_publ_section_title
;
 X-ray powder diffraction study on the modulated high temperature forms
 of SiO2 tridymite between 110 and 220 C
 Sample: superstructure, T = 115 C
;
_database_code_amcsd 0008553
_chemical_compound_source 'Synthetic'
_chemical_formula_sum 'Si O2'
_cell_length_a 26.1753
_cell_length_b 4.98437
_cell_length_c 8.2006
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 1069.911
_exptl_crystal_density_diffrn      2.238
_symmetry_space_group_name_H-M 'P 21 21 21'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '-x,1/2+y,1/2-z'
  '1/2+x,1/2-y,-z'
  '1/2-x,-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   0.13890   0.51100   0.69490   0.03730
Si2   0.14000   0.39100   0.32920   0.03730
Si3   0.19440   0.88800   0.19930   0.03730
Si4   0.19480   0.01900   0.83020   0.03730
Si5   0.02870   0.39500   0.18670   0.03730
Si6   0.02830   0.51000   0.81580   0.03730
O1   0.19660  -0.04300   0.01530   0.06020
O2   0.14910   0.45700   0.51030   0.06020
O3   0.08230   0.42900   0.27780   0.06020
O4   0.08140   0.56800   0.72990   0.06020
O5   0.25020   0.08000   0.77040   0.06020
O6   0.15710   0.26000   0.80020   0.06020
O7   0.17570   0.58300   0.22620   0.06020
O8   0.15700   0.08700   0.29020   0.06020
O9   0.17290   0.76600   0.73300   0.06020
O10   0.46340   0.54100   0.50210   0.06020
O11   0.49060   0.90500   0.72340   0.06020
O12   0.49600   0.72600   0.21240   0.06020