data_global _chemical_name_mineral 'Bertrandite' loop_ _publ_author_name 'Downs J W' 'Ross F K' _journal_name_full 'American Mineralogist' _journal_volume 72 _journal_year 1987 _journal_page_first 979 _journal_page_last 983 _publ_section_title ; Neutron-diffraction study of bertrandite Note: O2y has been corrected ; _database_code_amcsd 0001126 _chemical_formula_sum 'Si2 Be4 H2 O9' _cell_length_a 8.7135 _cell_length_b 15.268 _cell_length_c 4.5683 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 607.756 _exptl_crystal_density_diffrn 2.604 _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 Si 0.32510 0.11410 0.65400 Be1 0.17260 0.05249 0.15620 Be2 0.32640 0.22023 0.15090 H1 0.00000 0.20060 0.42030 H2 0.50000 0.36750 0.45300 O1 0.28990 0.12430 0.00000 O2 0.20950 0.04300 0.50650 O3 0.29380 0.20910 0.50120 O4 0.50000 0.08470 0.59160 O5 0.50000 0.25530 0.08770 O6 0.00000 0.08760 0.09780 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 Si 0.01030 0.00300 0.00900 -0.00080 -0.00040 0.00000 Be1 0.01040 0.00540 0.01070 0.00080 -0.00070 -0.00060 Be2 0.01260 0.00590 0.01110 0.00030 -0.00050 0.00130 H1 0.02100 0.02890 0.03510 0.00000 0.00000 -0.01760 H2 0.02950 0.02500 0.04070 0.00000 0.00000 -0.01530 O1 0.01360 0.00420 0.00960 -0.00150 0.00180 -0.00050 O2 0.01260 0.00530 0.01010 -0.00200 -0.00120 0.00030 O3 0.01530 0.00470 0.00990 0.00150 -0.00600 0.00050 O4 0.00770 0.00920 0.01720 0.00000 0.00000 -0.00270 O5 0.01050 0.01010 0.01580 0.00000 0.00000 0.00280 O6 0.01220 0.01040 0.01370 0.00000 0.00000 0.00110