data_global _chemical_name_mineral 'Bertrandite' loop_ _publ_author_name 'Hazen R M' 'Au A Y' _journal_name_full 'Physics and Chemistry of Minerals' _journal_volume 13 _journal_year 1986 _journal_page_first 69 _journal_page_last 78 _publ_section_title ; High-pressure crystal chemistry of phenakite (Be2SiO4) and bertrandite (Be4Si2O7(OH)2) Sample: P = 41 kbar Note: y-coordinate of O3 altered ; _database_code_amcsd 0007377 _chemical_formula_sum 'Be4 Si2 O9 H2' _cell_length_a 8.587 _cell_length_b 14.912 _cell_length_c 4.5901 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 587.759 _exptl_crystal_density_diffrn 2.692 _symmetry_space_group_name_H-M 'C m c 21' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2+x,1/2+y,z' 'x,-y,1/2+z' '1/2+x,1/2-y,1/2+z' '-x,y,z' '1/2-x,1/2+y,z' '-x,-y,1/2+z' '1/2-x,1/2-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 Be1 0.17230 0.05450 0.13600 0.01013 Be2 0.32970 0.22330 0.06500 0.00633 Si 0.32700 0.11280 0.64990 0.00570 O1 0.29560 0.12330 0.00000 0.01013 O2 0.20480 0.04430 0.50340 0.01013 O3 0.29900 0.20860 0.48460 0.01393 O4 0.00000 0.57960 0.58800 0.00887 O-H1 0.00000 0.76280 0.05330 0.00633 O-H2 0.00000 0.09470 0.07620 0.00760