data_global _chemical_name_mineral 'Nepheline' loop_ _publ_author_name 'Angel R J' 'Gatta G C' 'Boffa Ballaran T' 'Carpenter M A' _journal_name_full 'The Canadian Mineralogist' _journal_volume 46 _journal_year 2008 _journal_page_first 1465 _journal_page_last 1476 _publ_section_title ; The mechanism of coupling in the modulated structure of nepheline Note: natural sample Note: T = 200 K ; _database_code_amcsd 0006203 _chemical_compound_source 'Snipe River, Tambani, Malawi' _chemical_formula_sum 'K.57 Na3.24 (Al3.84 Si4.16) O16' _cell_length_a 9.9890 _cell_length_b 9.9890 _cell_length_c 8.3687 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 723.157 _exptl_crystal_density_diffrn 2.632 _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 0.00340 0.57000 0.02800 Na1 0.00000 0.00000 0.00340 0.24000 0.02800 Na2 0.55450 0.99720 0.50810 1.00000 0.02100 Al1 0.66667 0.33333 0.70140 0.48000 0.01200 Si1 0.66667 0.33333 0.70140 0.52000 0.01200 Al2 0.66667 0.33333 0.31340 0.48000 0.01300 Si2 0.66667 0.33333 0.31340 0.52000 0.01300 Al3 0.90610 0.66600 0.82230 0.48000 0.01300 Si3 0.90610 0.66600 0.82230 0.52000 0.01300 Al4 0.90680 0.66750 0.19590 0.48000 0.01100 Si4 0.90680 0.66750 0.19590 0.52000 0.01100 O1 0.66200 0.28580 0.50150 0.33333 0.02800 O2 0.97340 0.68300 0.00270 1.00000 0.03300 O3 0.82690 0.47750 0.25160 1.00000 0.03700 O4 0.83730 0.48960 0.76290 1.00000 0.03300 O5 0.77360 0.71450 0.82490 1.00000 0.01800 O6 0.77650 0.73300 0.20110 1.00000 0.02100