data_9004540
_chemical_name 'Calciotantite'
loop_
_publ_author_name
'Cooper M A'
'Hawthorne F C'
'Cerny P'
_journal_name_full "The Canadian Mineralogist"
_journal_volume 37
_journal_year 1999
_journal_page_first 1289
_journal_page_last 1294
_publ_section_title
;
 Ta-Nb order in the crystal structure of niobium-rich calciotantite
;
_chemical_formula_sum '(Ta2.821 Nb1.179) Ca O11'
_cell_length_a 6.2261
_cell_length_b 6.2261
_cell_length_c 12.280
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 120
_cell_volume 412.250
_symmetry_space_group_name_H-M 'P 63 2 2'
loop_
_symmetry_equiv_pos_as_xyz
  'x,y,z'
  'x,x-y,1/2-z'
  'x-y,x,1/2+z'
  'y,x,-z'
  '-y,x-y,z'
  '-x+y,y,1/2-z'
  '-x,-y,1/2+z'
  '-x,-x+y,-z'
  '-x+y,-x,z'
  '-y,-x,1/2-z'
  'y,-x+y,1/2+z'
  'x-y,-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
_atom_site_Uiso_or_equiv
Ta1   0.35938   0.35938   0.50000   0.69800   0.00760
Nb1   0.35938   0.35938   0.50000   0.30200   0.00760
Ta2   0.33333   0.66667   0.25000   0.72700   0.00820
Nb2   0.33333   0.66667   0.25000   0.27300   0.00820
Ca   0.66667   0.33333   0.25000   1.00000   0.00650
O1   0.37570   0.43040   0.34400   1.00000   0.00970
O2   0.75320   0.75320   0.50000   1.00000   0.01310
O3   0.33333   0.66667   0.53390   1.00000   0.00920