data_global
_chemical_name_mineral 'Phase-B-superhydrous'
loop_
_publ_author_name
'Pacalo R E G'
'Parise J B'
_journal_name_full 'American Mineralogist'
_journal_volume 77 
_journal_year 1992
_journal_page_first 681
_journal_page_last 684
_publ_section_title
;
 Crystal structure of superhydrous B, a hydrous magnesium silicate synthesized at
 1400 C and 20 GPa
;
_database_code_amcsd 0001483
_chemical_formula_sum 'Si3 Mg10 O18 H4'
_cell_length_a 5.0894
_cell_length_b 13.968
_cell_length_c 8.6956
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 618.159
_exptl_crystal_density_diffrn      3.327
_symmetry_space_group_name_H-M 'P n n m'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2-y,1/2+z'
  '1/2-x,1/2+y,1/2-z'
  '1/2-x,1/2+y,1/2+z'
  '1/2+x,1/2-y,1/2-z'
  'x,y,-z'
  '-x,-y,z'
  '-x,-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
Si1   0.50000   0.00000   0.00000   0.00443
Si2   0.48601   0.37652   0.00000   0.00367
Mg1   0.16941   0.17351   0.00000   0.00684
Mg2   0.15831   0.32346   0.32380   0.00671
Mg3   0.50000   0.50000   0.32127   0.00507
Mg4   0.50000   0.00000   0.34189   0.00545
O1   0.33221   0.41318   0.15612   0.00583
O2   0.49309   0.25923   0.00000   0.00545
O3   0.79141   0.41450   0.00000   0.00595
O4   0.35640   0.07307   0.14464   0.00519
O-h5  -0.01745   0.25185   0.15920   0.00773
O6   0.19568  -0.07921   0.00000   0.00646
H1  -0.07690   0.30260   0.10850   0.05446