data_global _chemical_name_mineral 'Nierite' loop_ _publ_author_name 'Yang P' 'Fun H-K' 'Rahman I A' 'Saleh M I' _journal_name_full 'Ceramics International' _journal_volume 21 _journal_year 1995 _journal_page_first 137 _journal_page_last 142 _publ_section_title ; Two phase refinements of the structures of a-Si3N4 and B-Si3N4 made from rice husk by Rietveld analysis Sample: Alpha phase Note: changed N4 location to match reported bond distances ; _database_code_amcsd 0012185 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'Si3 N4' _cell_length_a 7.7650 _cell_length_b 7.7650 _cell_length_c 5.6275 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 293.852 _exptl_crystal_density_diffrn 3.171 _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_U_iso_or_equiv Si1 0.51060 0.08150 0.19040 0.00925 Si2 0.16580 0.25200 -0.01680 0.00684 N1 0.00000 0.00000 -0.02900 0.00329 N2 0.33333 0.66667 0.63400 0.00380 N3 0.34880 -0.03830 -0.02200 0.01013 N4 0.30920 0.35460 0.23000 0.00127