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 = 1 bar
;
_database_code_amcsd 0007375
_chemical_formula_sum 'Be4 Si2 O9 H2'
_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
_atom_site_U_iso_or_equiv
Be1   0.17350   0.05270   0.16280   0.00570
Be2   0.32640   0.22030   0.15170   0.00608
Si   0.32540   0.11440   0.65230   0.00266
O1   0.28970   0.12440   0.00000   0.00481
O2   0.21010   0.04310   0.50740   0.00393
O3   0.29340   0.20930   0.50240   0.00532
O4   0.00000   0.58520   0.59510   0.00583
O-H1   0.00000   0.75530   0.08860   0.00684
O-H2   0.00000   0.08720   0.09930   0.00671
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
Be1 0.00923 0.00590 0.00211 -0.00034 0.00907 0.00177
Be2 0.00577 0.00590 0.00613 0.00202 0.00847 -0.00848
Si 0.00365 0.00307 0.00116 0.00054 0.00101 -0.00071
O1 0.00962 0.00354 0.00190 -0.00135 -0.00040 0.00035
O2 0.00615 0.00354 0.00201 0.00000 -0.00181 0.00035
O3 0.01039 0.00354 0.00148 0.00202 0.00000 -0.00035
O4 0.00308 0.00590 0.00846 0.00000 0.00000 -0.00177
O-H1 0.00500 0.00827 0.00698 0.00000 0.00000 0.00318
O-H2 0.00654 0.00945 0.00412 0.00000 0.00000 0.00283