[Wien] Error in wien2wannier for spin orbit coupling case

[Elias Assmann]

On 07/05/2016 07:18 PM, Niraj Aryal wrote:
> However, there is something serious thing I am encountering. When I do
> wannier90 calculation after finding case.mmn, case.amn and case.eig (up
> and down spins are added using w2waddsp), it gives me negative spread
> for Omega I e.g:
> 
>          Spreads (Ang^2)       Omega I      = -2549.235637370
>         ================       Omega D      =  1558.555122007
>                                Omega OD     =  3178.612948567
>     Final Spread (Ang^2)       Omega Total  =  2187.932433204
> 
> But we know that the spread has to be positive because it is expectation
> value of (r- <r>)^2 . I found similar post here:
> http://mailman.qe-forge.org/pipermail/wannier/2008-September/000199.html

Hm, I do not recall ever seeing negative values for the Ω components.
For completeness, note that the expectation value corresponds to the
*total* Ω; but nonetheless Ω_I must be nonnegative also on its own.
Also, your Ω_D and Ω_OD look very large.  (Typically, they should be
small compared to Ω_I.)

> Since Omega I is only calculated from the case.mmn file, I suspect that
> there is some problem in doing so.

As Jonathan noted in the e-mail you linked, this is the case for an
isolated group of bands (no disentanglement).  (This is not to say that
the error is not on the wien2wannier side, which it almost surely is.)

When you mention `w2waddsp`, does that mean you ran that program
manually?  You should not need to do that, it is called by `x wannier90
-so`.  Did you follow the procedure outlined in the wiki
<https://github.com/wien2wannier/wien2wannier/wiki/wien2wannier-with-SOC>?

If the problem persists, I can try it myself, but please give me any
parameters I need, i.e. anything that differs from

init -b -sp
runsp
initso
runsp -so

and the bands and initial projections you used.


	Elias

-- 
Elias Assmann

Wien2Wannier: maximally localized Wannier functions
              from linearized augmented plane waves

                     http://wien2wannier.github.io/
      https://github.com/wien2wannier/wien2wannier/

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