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 = 6.108 GPa ; _database_code_amcsd 0004426 _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 9.6189 _cell_length_b 9.6189 _cell_length_c 8.1423 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 652.422 _exptl_crystal_density_diffrn 2.917 _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 -0.00730 0.54000 0.01710 NaK 0.00000 0.00000 -0.00730 0.24000 0.01710 CaK 0.00000 0.00000 -0.00730 0.03000 0.01710 Na 0.55850 0.00022 0.50270 1.00000 0.01690 AlT1 0.66667 0.33333 0.70282 1.00000 0.00850 SiT2 0.66667 0.33333 0.29904 1.00000 0.00890 SiT3 0.92093 0.67173 0.81891 1.00000 0.00810 AlT4 0.92279 0.67442 0.18671 1.00000 0.00730 O1 0.66667 0.33333 0.49570 1.00000 0.03550 O2 0.00916 0.70138 -0.00360 1.00000 0.01380 O3 0.83600 0.47420 0.22370 1.00000 0.01720 O4 0.84860 0.48610 0.76320 1.00000 0.01750 O5 0.77757 0.71312 0.83270 1.00000 0.01070 O6 0.78680 0.73990 0.17980 1.00000 0.01350