Error with I2/c space group

[Dan Lowry]

I have a .cif file generated from a refinement using Jade 2010 that when opened with Vesta does not plot the atoms in the correct locations.  In the cif file the multiplicity is not in agreement with what is generated with Vesta (

.cif;

loop_
 _atom_site_label
 _atom_site_type_symbol
 _atom_site_symmetry_multiplicity

 _atom_site_occupancy
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_B_iso_or_equiv
 _atom_site_thermal_displace_type
 La1  La+3 4   1.0   0.0     0.62926   0.25     0.10438  Biso
 Nb1  Nb+5 4   1.0   0.0     0.10426   0.25     0.0      Biso
 O1   O-2  8   1.0   0.2328   0.0355   0.0702   0.5      Biso
O2   O-2  8   1.0   0.17091  0.21091  0.49531  0.5      Biso

 Vesta;

Lattice parameters
   a        b        c       alpha    beta     gamma
 5.56534 11.52081  5.20222  90.0000  94.0940  90.0000
Unit-cell volume = 332.700776 Å^3
Structure parameters
                       x          y          z          Occ.     B    Site    Sym.
   1 La  La1         0.00000    0.62926    0.25000    1.000    0.104    8f       1
   2 Nb  Nb1         0.00000    0.10426    0.25000    1.000    1.000    8f       1
   3 O   O1          0.23280    0.03550    0.07020    1.000    0.500    8f       1
   4 O   O2          0.17091    0.21091    0.49531    1.000    0.500    8f       1

As you can see here in the cif file for La and Nb the multiplicity should be 4 (specifically 4e for the space group) but when VESTA reads the file it plots as 8f. I have tried manually building the unit cell but encounter the same problem with La and Nb being plotted as 8f and not 4e. 

Is there a solution to correct this error?

[Philip Howie]

Hi Dan,

Which space group are you actually using?  I2/c is equivalent to C2/c, unless I'm mistaken, which is spacegroup 15 and VESTA's setting 1.  When I manually input the data you've supplied, I get the correct multiplicities - .cif file attached.

Hope that helps,

Phil

[Dan Lowry]

Philip if I load the cif file you created I get the following structure;

In this structure the Nb atoms are in the correct locations however, the La atoms should be mirrored across the middle of the cell (as below)

To generate this I edited my cif file using an icsd file as reference to the following;

_cell_length_a                     5.56534
_cell_length_b                     11.52081
_cell_length_c                     5.20222
_cell_angle_alpha                  90.
_cell_angle_beta                   94.094
_cell_angle_gamma                  90.
_cell_volume                       332.7
_cell_formula_units_Z              4
_symmetry_space_group_name_H-M     'I 1 2/c 1'
_symmetry_Int_Tables_number        15
loop_
_symmetry_equiv_pos_site_id
_symmetry_equiv_pos_as_xyz
  1 '-x, y, -z+1/2'
  2 '-x, -y, -z'
  3 'x, -y, z+1/2'
  4 'x, y, z'
  5 '-x+1/2, y+1/2, -z'
  6 '-x+1/2, -y+1/2, -z+1/2'
  7 'x+1/2, -y+1/2, z'
  8 'x+1/2, y+1/2, z+1/2'
loop_
_atom_type_symbol
_atom_type_oxidation_number
La3+ 3
Nb5+ 5
O2- -2

loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_symmetry_multiplicity
_atom_site_occupancy
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_B_iso_or_equiv
_atom_site_thermal_displace_type

La1 La3+ 4 1.0   0.0     0.62926   0.25     0.10438  Biso
Nb1 Nb5+ 4 1.0   0.0     0.10426   0.25     0.0      Biso
O1  O2-  8 1.0   0.2328   0.0355   0.0702   0.5      Biso
O2  O2-  8 1.0   0.17091  0.21091  0.49531  0.5      Biso