data_global _chemical_name_mineral 'Hydrogen' loop_ _publ_author_name 'Mao H K' 'Jephcoat A P' 'Hemley R J' 'Finger L W' 'Zha C S' 'Hazen R M' 'Cox D E' _journal_name_full 'Science' _journal_volume 239 _journal_year 1988 _journal_page_first 1131 _journal_page_last 1133 _publ_section_title ; Synchrotron X-ray diffraction measurements of single-crystal hydrogen to 26.5 Gigapascals Sample: at P = 21.4 GPa, T = 300 K ; _database_code_amcsd 0015435 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'H' _cell_length_a 2.308 _cell_length_b 2.308 _cell_length_c 3.703 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 17.083 _exptl_crystal_density_diffrn 0.196 _symmetry_space_group_name_H-M 'P 63/m m c' loop_ _space_group_symop_operation_xyz 'x,y,z' '-x,-x+y,1/2+z' 'x,x-y,1/2-z' '-x+y,-x,1/2-z' 'x-y,x,1/2+z' '-y,-x,z' 'y,x,-z' 'y,-x+y,-z' '-y,x-y,z' 'x-y,-y,1/2+z' '-x+y,y,1/2-z' 'x,y,1/2-z' '-x,-y,1/2+z' 'x,x-y,z' '-x,-x+y,-z' 'x-y,x,-z' '-x+y,-x,z' 'y,x,1/2+z' '-y,-x,1/2-z' '-y,x-y,1/2-z' 'y,-x+y,1/2+z' '-x+y,y,z' 'x-y,-y,-z' '-x,-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z H 0.33333 0.66667 0.25000