data_global _chemical_name_mineral 'Nepheline' loop_ _publ_author_name 'Gatta G D' 'Angel R J' _journal_name_full 'American Mineralogist' _journal_volume 92 _journal_year 2007 _journal_page_first 1446 _journal_page_last 1455 _publ_section_title ; Elastic behavior and pressure-induced structural evolution of nepheline: Implications for the nature of the modulated superstructure Sample: P = .0001 GPa, in air ; _database_code_amcsd 0004422 _chemical_compound_source 'intrusive aplite of Snipe River, Tambani, Nyasaland, Malawi' _chemical_formula_sum 'K.54 Na3.24 Ca.03 Al4 Si4 O16' _cell_length_a 9.9995 _cell_length_b 9.9995 _cell_length_c 8.3766 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 725.362 _exptl_crystal_density_diffrn 2.624 _symmetry_space_group_name_H-M 'P 63' loop_ _space_group_symop_operation_xyz 'x,y,z' 'x-y,x,1/2+z' '-y,x-y,z' '-x,-y,1/2+z' '-x+y,-x,z' 'y,-x+y,1/2+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 K 0.00000 0.00000 0.00410 0.54000 0.03296 NaK 0.00000 0.00000 0.00410 0.24000 0.03296 CaK 0.00000 0.00000 0.00410 0.03000 0.03296 Na 0.55412 0.99724 0.50845 1.00000 0.02537 AlT1 0.66667 0.33333 0.70194 1.00000 0.01271 SiT2 0.66667 0.33333 0.31362 1.00000 0.01423 SiT3 0.90568 0.66614 0.82276 1.00000 0.01378 AlT4 0.90645 0.66759 0.19630 1.00000 0.01235 O1 0.66190 0.28910 0.50178 0.33333 0.03350 O2 0.97288 0.68347 0.00309 1.00000 0.03350 O3 0.82649 0.47750 0.25170 1.00000 0.03807 O4 0.83665 0.48973 0.76444 1.00000 0.03390 O5 0.77365 0.71475 0.82462 1.00000 0.02064 O6 0.77607 0.73287 0.20149 1.00000 0.02315