data_global _chemical_name_mineral 'Urea' loop_ _publ_author_name 'Swaminathan S' 'Craven B M' _journal_name_full 'Acta Crystallographica, Section B' _journal_volume 40 _journal_year 1984 _journal_page_first 300 _journal_page_last 306 _publ_section_title ; The crystal structure and molecular thermal motion of urea at 12, 60 and 123 K from neutron diffraction Note: neutron data, T = 12 K ; _database_code_amcsd 0020674 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'C H4 N2 O' _cell_length_a 5.565 _cell_length_b 5.565 _cell_length_c 4.684 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 145.060 _exptl_crystal_density_diffrn 1.375 _symmetry_space_group_name_H-M 'P -4 21 m' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2-y,1/2-x,z' 'y,-x,-z' '1/2-x,1/2+y,-z' '-x,-y,z' '1/2+y,1/2+x,z' '-y,x,-z' '1/2+x,1/2-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z C 0.00000 0.50000 0.32600 H1 0.25750 0.75750 0.28270 H2 0.14410 0.64410 -0.03800 N 0.14590 0.64590 0.17660 O 0.00000 0.50000 0.59530 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 C 0.00630 0.00630 0.00350 0.00020 0.00000 0.00000 H1 0.02770 0.02770 0.01850 -0.01430 -0.00290 -0.00290 H2 0.02940 0.02940 0.01160 -0.00940 0.00150 0.00150 N 0.01130 0.01130 0.00590 -0.00520 0.00040 0.00040 O 0.00870 0.00870 0.00320 0.00020 0.00000 0.00000