data_1001274
_chemical_name_systematic          'POTASSIUM BARIUM SILICOTANTALATE *'
_chemical_formula_structural       'K4 BA TA6 SI4 O26'
_chemical_formula_sum              'Ba K4 O26 Si4 Ta6'
_publ_section_title
;
Silicotantalates et siliconiobates non-stoechiometriques: les composes
K~6-2x~ Ba~x~ Ta~6~ Si~4~ O~26~ (0<x<3) et K~8~ M~14~ Si~4~ O~47~ (M =
Ta, Nb)
;
loop_
_publ_author_name
  'Choisnet, J'
  'Nguyen, N'
  'Raveau, B'
_journal_name_full                 'Materials Research Bulletin'
_journal_coden_ASTM                MRBUAC
_journal_volume                    12
_journal_year                      1977
_journal_page_first                91
_journal_page_last                 96
_cell_length_a                     9.047
_cell_length_b                     9.047
_cell_length_c                     7.81
_cell_angle_alpha                  90
_cell_angle_beta                   90
_cell_angle_gamma                  120
_cell_volume                       553.6
_cell_formula_units_Z              1
_symmetry_space_group_name_H-M     'P -6 2 m'
_symmetry_Int_Tables_number        189
_symmetry_cell_setting             hexagonal
loop_
_symmetry_equiv_pos_as_xyz
  'x,y,z'
  '-y,x-y,z'
  'y-x,-x,z'
  'x,y,-z'
  '-y,x-y,-z'
  'y-x,-x,-z'
  'y,x,z'
  'x-y,-y,z'
  '-x,y-x,z'
  'y,x,-z'
  'x-y,-y,-z'
  '-x,y-x,-z'
loop_
_atom_type_symbol
_atom_type_oxidation_number
  Ba2+   2.000
  K1+    1.000
  Ta5+   5.000
  Si4+   4.000
  O2-   -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
  Ba1   Ba2+   3 g 0.586 0. 0.5 0.3333  0 d
  K1    K1+    3 g 0.586 0. 0.5 0.6667  0 d
  K2    K1+    3 f 0.61 0. 0. 0.6667  0 d
  Ta1   Ta5+   6 i 0.239 0. 0.249 1.  0 d
  Si1   Si4+   4 h 0.3333 0.6667 0.208 1.  0 d
  O1    O2-    2 c 0.3333 0.6667 0. 1.  0 d
  O2    O2-    3 f 0.262 0. 0. 1.  0 d
  O3    O2-    6 i 0.811 0. 0.269 1.  0 d
  O4    O2-   12 l 0.5 0.176 0.289 1.  0 d
  O5    O2-    3 g 0.242 0. 0.5 1.  0 d
_refine_ls_R_factor_all            0.061