data_global _chemical_name_mineral 'Selenium' loop_ _publ_author_name 'Keller R' 'Holzapfel W B' 'Schulz H' _journal_name_full 'Physical Review' _journal_volume B16 _journal_year 1977 _journal_page_first 4404 _journal_page_last 4412 _publ_section_title ; Effect of pressure on the atom positions in Se and Te Sample: at P = 6.57 GPa Note: known as alpha phase with trigonal structure ; _database_code_amcsd 0015165 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'Se' _cell_length_a 3.846 _cell_length_b 3.846 _cell_length_c 5.095 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 65.267 _exptl_crystal_density_diffrn 6.027 _symmetry_space_group_name_H-M 'P 31 2 1' loop_ _space_group_symop_operation_xyz 'x,y,z' 'y,x,-z' '-y,x-y,1/3+z' '-x,-x+y,1/3-z' '-x+y,-x,2/3+z' 'x-y,-y,2/3-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z Se 0.24930 0.00000 0.33333