data_global _chemical_name_mineral 'Nierite' loop_ _publ_author_name 'Kohatsu I' 'McCauley J W' _journal_name_full 'Materials Research Bulletin' _journal_volume 9 _journal_year 1974 _journal_page_first 917 _journal_page_last 920 _publ_section_title ; Re-examination of the crystal structure of alpha-Si3N4 ; _database_code_amcsd 0014238 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'Si2.925 N3.99' _cell_length_a 7.766 _cell_length_b 7.766 _cell_length_c 5.615 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 293.275 _exptl_crystal_density_diffrn 3.126 _symmetry_space_group_name_H-M 'P 3 1 c' loop_ _space_group_symop_operation_xyz 'x,y,z' 'x-y,-y,1/2+z' '-y,x-y,z' 'y,x,1/2+z' '-x+y,-x,z' '-x,-x+y,1/2+z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_occupancy Si1 0.51300 0.43050 0.65800 0.96000 Si2 0.16800 0.91500 0.45040 0.99000 N1 0.61240 0.95920 0.43430 1.00000 N2 0.31990 0.00460 0.70450 1.00000 N3 0.66667 0.33333 0.60150 1.00000 N4 0.00000 0.00000 0.45200 0.98000 loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_12 _atom_site_aniso_U_13 _atom_site_aniso_U_23 Si1 0.01833 0.01329 0.01294 0.00733 0.00268 0.00113 Si2 0.01833 0.01627 0.01022 0.00871 0.00727 -0.00090 N1 0.00412 0.00985 0.03849 -0.00069 0.00536 0.01282 N2 0.00367 0.00321 0.03402 -0.00390 0.00497 0.00230 N3 0.00550 0.00550 0.01182 0.00275 0.00000 0.00000 N4 0.01467 0.01467 0.02859 0.00733 0.00000 0.00000