data_global _chemical_name_mineral 'Wesselsite' loop_ _publ_author_name 'Knight K S' 'Henderson C M B' _journal_name_full 'European Journal of Mineralogy' _journal_volume 19 _journal_year 2007 _journal_page_first 189 _journal_page_last 200 _publ_section_title ; Structural basis for the anomalous low-temperature thermal expansion behavior of the gillespite-structured phase Ba0.5Sr0.5CuSi4O10 Sample: T = 200 K ; _database_code_amcsd 0007212 _chemical_formula_sum '(Ba.5 Sr.5) Cu Si4 O10' _cell_length_a 7.39447 _cell_length_b 7.39447 _cell_length_c 15.8534 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 866.835 _exptl_crystal_density_diffrn 3.436 _symmetry_space_group_name_H-M 'P 4/n c c' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2-y,1/2-x,1/2+z' '1/2+y,1/2+x,1/2-z' '1/2+y,-x,-z' '1/2-y,x,z' 'x,1/2-y,1/2+z' '-x,1/2+y,1/2-z' '1/2+x,1/2+y,-z' '1/2-x,1/2-y,z' 'y,x,1/2+z' '-y,-x,1/2-z' '-y,1/2+x,-z' 'y,1/2-x,z' '1/2-x,y,1/2+z' '1/2+x,-y,1/2-z' '-x,-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_occupancy _atom_site_U_iso_or_equiv Ba 0.25000 0.75000 0.00000 0.50000 0.05760 Sr 0.25000 0.75000 0.00000 0.50000 0.05760 Cu 0.25000 0.25000 0.09190 1.00000 0.07580 Si 0.51250 0.93370 0.15204 1.00000 0.03440 O1 0.45320 0.98630 0.24590 0.50000 0.09700 O2 0.71830 -0.00020 0.13358 1.00000 0.07960 O3 0.37440 0.02420 0.08828 1.00000 0.08540