data_1011176 _chemical_name_systematic 'Silicon oxide - $-alpha' _chemical_name_mineral 'Quartz low' _chemical_formula_structural 'Si O2' _chemical_formula_sum 'O2 Si' _publ_section_title ; Die Kristallstruktur von Tiefquarz Si O2 und Aluminiumorthoarsenat Al As O4 ; _publ_author_name 'Machatschki, F' _journal_name_full ; Zeitschrift fuer Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie (-144,1977) ; _journal_coden_ASTM ZEKGAX _journal_volume 94 _journal_year 1936 _journal_page_first 222 _journal_page_last 230 _cell_length_a 4.9 _cell_length_b 4.9 _cell_length_c 5.4 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 112.3 _cell_formula_units_Z 3 _exptl_crystal_density_meas 2.66 _symmetry_space_group_name_H-M 'P 32 2 1 S' _symmetry_Int_Tables_number 154 _symmetry_cell_setting trigonal loop_ _symmetry_equiv_pos_as_xyz 'x,y,z' 'y,x,2/3-z' '-y,x-y,2/3+z' '-x,y-x,1/3-z' 'y-x,-x,1/3+z' 'x-y,-y,-z' loop_ _atom_type_symbol _atom_type_oxidation_number Si4+ 4.000 O2- -2.000 loop_ _atom_site_label _atom_site_type_symbol _atom_site_symmetry_multiplicity _atom_site_Wyckoff_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_occupancy _atom_site_attached_hydrogens _atom_site_calc_flag Si1 Si4+ 3 a 0.469(3) 0. 0. 1. 0 d O1 O2- 6 c 0.403(6) 0.253(6) 0.122(6) 1. 0 d