data_2002341
_chemical_name_systematic
;
Heptastrontium diniobium(IV) tetraniobium oxide
;
_chemical_formula_structural       'Sr7 Nb6 O21'
_chemical_formula_sum              'Nb6 O21 Sr7'
_publ_section_title
;
Ein neues gemischtvalentes Oxoniobat: Sr7 (Nb4+)2 (Nb5+)4 O21 = Sr1.167
Nb O3.5.
;
loop_
_publ_author_name
  'Schueckel, K'
  'Mueller-Buschbaum, Hk'
_journal_name_full
;
Zeitschrift fuer Anorganische und Allgemeine Chemie
;
_journal_volume                    523
_journal_year                      1985
_journal_page_first                69
_journal_page_last                 75
_cell_length_a                     5.670(1)
_cell_length_b                     5.670(1)
_cell_length_c                     48.364(13)
_cell_angle_alpha                  90
_cell_angle_beta                   90
_cell_angle_gamma                  120
_cell_volume                       1346.5
_cell_formula_units_Z              3
_symmetry_space_group_name_H-M     'R -3 H'
_symmetry_Int_Tables_number        148
_symmetry_cell_setting             trigonal
loop_
_symmetry_equiv_pos_as_xyz
  'x,y,z'
  '-y,x-y,z'
  'y-x,-x,z'
  '-x,-y,-z'
  'y,y-x,-z'
  'x-y,x,-z'
  '1/3+x,2/3+y,2/3+z'
  '2/3+x,1/3+y,1/3+z'
  '1/3-y,2/3+x-y,2/3+z'
  '2/3-y,1/3+x-y,1/3+z'
  '1/3-x+y,2/3-x,2/3+z'
  '2/3-x+y,1/3-x,1/3+z'
  '1/3-x,2/3-y,2/3-z'
  '2/3-x,1/3-y,1/3-z'
  '1/3+y,2/3-x+y,2/3-z'
  '2/3+y,1/3-x+y,1/3-z'
  '1/3+x-y,2/3+x,2/3-z'
  '2/3+x-y,1/3+x,1/3-z'
loop_
_atom_type_symbol
_atom_type_oxidation_number
  Sr2+   2.000
  Nb4+   4.000
  Nb5+   5.000
  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
  Sr1   Sr2+   3 a 0. 0. 0. 1.  0 d
  Sr2   Sr2+   6 c 0. 0. 0.1503(1) 1.  0 d
  Sr3   Sr2+   6 c 0. 0. 0.2294(1) 1.  0 d
  Sr4   Sr2+   6 c 0. 0. 0.3804(1) 1.  0 d
  Nb1   Nb4+   6 c 0. 0. 0.0729(1) 1.  0 d
  Nb2   Nb5+   6 c 0. 0. 0.3063(1) 1.  0 d
  Nb3   Nb5+   6 c 0. 0. 0.4567(1) 1.  0 d
  O1    O2-    9 e 0. 0.5 0. 1.  0 d
  O2    O2-   18 f 0.329(6) 0.195(6) 0.044 1.  0 d
  O3    O2-   18 f 0.119(4) 0.336(4) 0.094 1.  0 d
  O4    O2-   18 f 0.457(6) 0.461(6) 0.142 1.  0 d
_refine_ls_R_factor_all            0.016