data_1011226
_chemical_name_systematic          'Diberyllium silicate'
_chemical_name_mineral             'Phenakite'
_chemical_formula_structural       'Be2 (Si O4)'
_chemical_formula_sum              'Be2 O4 Si'
_publ_section_title                'The structure of phenacite Be2 Si O4'
_publ_author_name                  'Bragg, L W'
_journal_name_full
;
Proceedings of the Royal Society of London, Series A: Mathematical and
Physical Sciences (76,1906-)
;
_journal_coden_ASTM                PRLAAZ
_journal_volume                    113
_journal_year                      1927
_journal_page_first                642
_journal_page_last                 657
_cell_length_a                     7.684
_cell_length_b                     7.684
_cell_length_c                     7.684
_cell_angle_alpha                  108.02
_cell_angle_beta                   108.02
_cell_angle_gamma                  108.02
_cell_volume                       366.8
_cell_formula_units_Z              6
_exptl_crystal_density_meas        2.98
_symmetry_space_group_name_H-M     'R -3 R'
_symmetry_Int_Tables_number        148
_symmetry_cell_setting             trigonal
loop_
_symmetry_equiv_pos_as_xyz
  'x,y,z'
  'y,z,x'
  'z,x,y'
  '-x,-y,-z'
  '-y,-z,-x'
  '-z,-x,-y'
loop_
_atom_type_symbol
_atom_type_oxidation_number
  Si4+   4.000
  O2-   -2.000
  Be2+   2.000
loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_symmetry_multiplicity
_atom_site_Wyckoff_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_attached_hydrogens
_atom_site_calc_flag
  Si1   Si4+   6 f 0.039 0.449 0.261 1.  0 d
  O1    O2-    6 f 0.158 0.463 0.13 1.  0 d
  O2    O2-    6 f -0.07 0.57 0.25 1.  0 d
  O3    O2-    6 f -0.121 0.214 0.157 1.  0 d
  O4    O2-    6 f 0.212 0.547 0.491 1.  0 d
  Be1   Be2+   6 f -1. -1. -1. 2.  0 dum