data_global
_chemical_name_mineral 'Weberite'
loop_
_publ_author_name
'Knop O'
'Cameron T S'
'Jochem K'
_journal_name_full 'Journal of Solid State Chemistry'
_journal_volume 43 
_journal_year 1982
_journal_page_first 213
_journal_page_last 221
_publ_section_title
;
 What is the true space group of weberite?
 Sample: I2mb refinement, T = ambient
 Note: z(F6) corrected
;
_database_code_amcsd 0013483
_chemical_compound_source 'Ivigtut, Greenland'
_chemical_formula_sum 'Na2 Mg Al F7'
_cell_length_a 7.051
_cell_length_b 9.968
_cell_length_c 7.285
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 512.022
_exptl_crystal_density_diffrn      2.987
_symmetry_space_group_name_H-M 'I 2 m b'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2+y,1/2+z'
  'x,1/2+y,1/2-z'
  '1/2+x,+y,-z'
  'x,-y,z'
  '1/2+x,1/2-y,1/2+z'
  'x,1/2-y,1/2-z'
  '1/2+x,-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
Na1   0.25440   0.00000   0.49540
Na2   0.00000   0.25000   0.75000
Mg   0.25220   0.00000   0.99900
Al   0.00250   0.25000   0.25000
F1   0.00430   0.00000   0.88640
F3   0.00420   0.16490   0.47090
F5   0.18740   0.13760   0.18130
F6   0.31920   0.13720   0.82060
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
Na1 0.01800 0.01910 0.05390 0.00000 -0.00450 0.00000
Na2 0.02130 0.03350 0.01460 0.00000 0.00000 0.00950
Mg 0.00730 0.00590 0.00680 0.00000 0.00080 0.00000
Al 0.00760 0.00670 0.00710 0.00000 0.00000 -0.00180
F1 0.00770 0.01870 0.01260 0.00000 0.00150 0.00000
F3 0.01800 0.01560 0.00940 -0.00110 -0.00090 0.00140
F5 0.01430 0.01350 0.01540 0.00180 0.00210 -0.00640
F6 0.01080 0.01170 0.01780 0.00480 0.00120 -0.00510