[Pw_forum] Real displacements from the complex eigenvectors

[Alexandr Fonari]

Dear Dr. Wang,

can you expand a little how you arrived to this results?
also in the panasis code I found this comment [1]:


here is the correct algorithm for making the eigenvectors
real:
abbreviated form: one needs to extend the supercell and multiply by phase factor
and add together as complex conjugates until they are real
(this is already implemented somewhere in isotropy--email stokes
more later... 

I don't understand where complex conjugate part comes from.

[1] http://danse.cacr.caltech.edu/packages/dev_danse_us/parnasis-0.5.tar.gz

thanks,
Alexandr.

> 
> From: xirainbow <nkxirainbow at gmail.com> Sent: Wednesday, June 5, 2013 8:50 PM wrote:
> Dear Alexandr Fonari:
>           I think the real displacement at q!=0  is : displacement =
> real(eigenvector*exp(i*k*r-omega*t)). real() means the real part,
> omega is frequency, t is time, r is the equilibrium position of atoms.
> 
> 
> On Thu, Jun 6, 2013 at 2:12 AM, A F <af3_pw_forum at yahoo.com> wrote:
> > Hello pw_forum,
> >
> > I have a question with regard to the normal modes at non G-point (q/=0).
> > As discussed previously [1], phase is random.
> > Thus my question is, how one can obtain displacements in real space from
> > those complex displacements?
> >
> >
> > 1. http://qe-forge.org/pipermail/pw_forum/2006-August/079408.html
> >
> > = = = = = = = = = =
> > Alexandr Fonari,
> > graduate student,
> > Georgia Institute of Technology.
> >
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> 
> 
> 
> -- 
> ____________________________________
> Hui Wang
> School of physics, Fudan University, Shanghai, China