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 after decompression ; _database_code_amcsd 0004428 _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 9.9907 _cell_length_b 9.9907 _cell_length_c 8.3695 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 723.472 _exptl_crystal_density_diffrn 2.631 _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 0.00350 0.54000 0.03448 NaK 0.00000 0.00000 0.00350 0.24000 0.03448 CaK 0.00000 0.00000 0.00350 0.03000 0.03448 Na 0.55414 0.99762 0.50785 1.00000 0.02594 AlT1 0.66667 0.33333 0.70209 1.00000 0.01355 SiT2 0.66667 0.33333 0.31353 1.00000 0.01392 SiT3 0.90606 0.66644 0.82291 1.00000 0.01334 AlT4 0.90620 0.66767 0.19635 1.00000 0.01306 O1 0.67080 0.29570 0.50080 0.33333 0.03480 O2 0.97316 0.68409 0.00228 1.00000 0.03106 O3 0.82600 0.47725 0.25143 1.00000 0.03600 O4 0.83662 0.48965 0.76565 1.00000 0.03280 O5 0.77305 0.71396 0.82379 1.00000 0.01929 O6 0.77664 0.73391 0.20013 1.00000 0.02300