[Wannier] large spreeds for some WFs

Arash A Mostofi mostofi at MIT.EDU
Fri Nov 24 17:37:11 CET 2006

Dear Hai-Ping

There are two things that might help:

(i) increase the number of conduction bands. If you're trying to obtain 
partially-occupied, out-of-plane p_z orbitals for your nanotube, you 
probably need to include bands that are at least 5eV or so above the Fermi 

(ii) use the projections to give the dientanglement algorithm a good 
starting guess, eg, an s-type orbital on each bond and a p_z orbital on 
each atom.


On Thu, 23 Nov 2006, lan haiping wrote:

> Dear All,
> I am trying to  study  disentanglement of wannier with nanotube (10 0) by
> including several conduction bands.
> There are some problems  that i didnot come to for the cases of only valence
> bands included.
> First , it takes me long time to reach the convergence thread for
> disentangle process. I just tried to tune dis_mix_ratio , but there is no
> much effect.  In my calculation, I had included 130 bands for disentangling
> 100 WFs, it would take about 4000 iterations to reach convergence no matter
> what dis_mix_ratio i set to.  This value is of course seriouly larger than
> the default value (200).
> Though there are a few parameters for disentanglement, i donot have much
> idea about
> energy window settings for disentanglement and frozen energy window. Could
> we just set dis_win_min to conduction bands' bottom in my semiconducting cnt
> case  ?  I also tried to set frozen energy window , but there was no much
> effect for improving convergence. Could  the proper frozen energy window
> improve convergence ?  and would you please tell how to set up frozen energy
> window properly ?
> Another question is about large spreads for some WFs after
> wannierise.Afterwannierise process, there are mainly 3 groups of
> spreads of WFs. Spreads of
> first group are around 0.6- 0.7,  while 1.6-2.4 are for second group. There
> are 2 WFs for third group, of  spreads around 7.0 ,which are great larger
> than  that of other two group. Does such result have proper physical meaning
> ?
> Any comments will be appreciated.     As far as i know, large spreads of WFs
> may not be suitable for tight binding calculation . Are there any methods or
> settings to obtain smaller spreads of  WFs ?
> Best Wishes,
> hai-ping

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