data_global
_chemical_name_mineral 'Birnessite'
loop_
_publ_author_name
'Post J E'
'Veblen D R'
_journal_name_full 'American Mineralogist'
_journal_volume 75 
_journal_year 1990
_journal_page_first 477
_journal_page_last 489
_publ_section_title
;
 Crystal structure determinations of synthetic sodium, magnesium and potassium
 birnessite using TEM and the Rietveld method
 sample is Na-birn
;
_database_code_amcsd 0001300
_chemical_formula_sum 'Mn O2.75 Na.29 H1.5'
_cell_length_a 5.174
_cell_length_b 2.850
_cell_length_c 7.336
_cell_angle_alpha 90
_cell_angle_beta 103.18
_cell_angle_gamma 90
_cell_volume 105.326
_exptl_crystal_density_diffrn      3.377
_symmetry_space_group_name_H-M 'C 1 2/m 1'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2+y,z'
  'x,-y,z'
  '1/2+x,1/2-y,z'
  '-x,y,-z'
  '1/2-x,1/2+y,-z'
  '-x,-y,-z'
  '1/2-x,1/2-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_U_iso_or_equiv
Mn   0.00000   0.00000   0.00000   1.00000   0.00633
O1   0.37600   0.00000   0.13300   1.00000   0.01267
Na   0.59500   0.00000   0.50000   0.14500   0.01900
Wat2   0.59500   0.00000   0.50000   0.30000   0.01900
Wat3   0.00000   0.00000   0.50000   0.15000   0.01900