[Wannier] Wannier function centers at wrong positions

[nicolas poilvert]

Dear Jan,

I see that in your input file that you use exactly 606 bands for 606 Wannier
Functions.
It would be good to maybe include more bands in your calculation and use the
disentanglement
procedure (look at the Wannier User Guide for that).
Also, if you cell is quite big, using random projections may not be optimal.
So if you have an
idea of what those Wannier Functions should be, there is definitely
advantage to input some
carefully chosen initial projections. In the random guess case, the code may
get stuck in a local
minimum that does not correspond to the proper physical minimum you seek.
As a final note, I would set the convergence threshold to 1.0d-7 at least to
both disentanglement
and wannierisation and use a lot of steps just in case (num_iter > 2000 and
dis_num_iter > 2000).

good luck,

Nicolas

On Fri, Apr 9, 2010 at 12:02 PM, Jan Felix Binder
<janfelix.binder at epfl.ch>wrote:

> Hello,
> I used the W90 code with PWscf (QE 4.1.2) to calculate MLWF for a
> amorphous structure (gamma point only, 234 atoms, 606 wf).
> All WF convered to reasonable values. Most of the centers are at the
> right positions, but approximately 10 centers hang somewhere around.
> What can be wrong?
>
> I add the imported lines of the input file:
>  gamma_only = .true.
> num_iter         =  100
> dis_num_iter     =  200
> conv_window = 10
> conv_noise_amp = 1
> conv_noise_num = 10
> dis_mix_ratio = 0.3
> guiding_centres = .true.
>
> iprint           =    2
> num_dump_cycles  =   10
> num_print_cycles =   10
>
> length_unit      =  Ang
>
> num_wann = 606
> num_bands=606
>
> exclude_bands : 607-614
>
> Begin Projections
> random
> End Projections
>
> translate_home_cell=.true.
> write_xyz=.true.
>
> begin unit_cell_cart
>  bohr
> 47.65304  0.00000  0.00000
>  0.00000 23.82652  0.00000
>  0.00000  0.00000 23.82652
> end unit_cell_cart
>
> Thank you for help!
> Felix Binder
>
> EPFL Lausanne
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>



-- 
POILVERT Nicolas
PhD candidate,
Dpt of Materials Science and Engineering
Massachusetts Institute of Technology
77, Massachusetts avenue
Cambridge, MA 02139
USA
work: (617) 452-4212
nicolas.poilvert at gmail.com
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