[Wannier] wannier WF and Hamiltonian

[Liping Chen]

Dear Aron,

Thanks for your quick reply!

About the initial projections, I always have problems. Now I'm doing the calculation on SiO2. Actually, I tried different initial projections. They gave similar results of "Omega Total  =   579.766631183", which means that the WF is extended over 3-4 unit cells (the lattice constant lc in three directions is 7.12 Ang). It shouldn't be like this, right? My supervisor thinks the WF should be localized in one unit cell. I don't know it's correct or not, since I've looked at the WF of GaAs in example01 of wannier90. It seems that the WF is not localized in one unit cell. If the WF is localized in one unit cell, does it mean that Omega Total should be close to the value of lc*lc? Is any principle to set the initial projections? It seems that num_wann should be consistent with the number of projections, since sometimes it says "too many projections" or "too less projections". Can you give some suggestions about the initial projections? Thanks!

Liping

----- Original Message -----
From: "szaboa" <szaboa at iis.ee.ethz.ch>
To: wannier at quantum-espresso.org
Sent: Thursday, January 30, 2014 3:02:18 PM
Subject: Re: [Wannier] wannier WF and Hamiltonian

Dear Liping Chen,

You should add an LWRITE_UNK = .TRUE. line in the INCAR file to make 
vasp produce those UNK files.

Regarding your second question: The matrix elements should be real 
indeed. As far as i know, having nonnegligible imaginary parts usually 
means that the program converged to a fals minimum. You should probably 
specify different initial projections.

Best regards,
Aron Szabo

On 2014-01-30 19:37, Liping Chen wrote:
> Dear wannier users,
>
> I want to show the wannier WF with xcrysden. I find that there is an
> example (the first one) in wannier90 tutorial. It seems that the UNK*
> files should to be prepared in advance. It's easy to get them by
> PWSCF. But now I'm using VASP. I've tried to check the WAVECAR from
> VASP. It seems that the WAVECAR for the coefficients is written like
> this:
> ##################################################
> do ik=1,num_kpoints
>   do iband=1,nband
>     do iplane=1,nplane
>       coeff(iplane,iband) ! write the coefficients
>     enddo
>   enddo
> enddo
> ##################################################
> The number of plane waves (nplane) is not the same for all the
> kpoints (ik). I don't know the relationship the number of plane waves
> and the ngx, ngy, ngz written in the beginning of the UNK* files. How
> to get the UNK* files from VASP so that I can get the WF from wannier
> and then plot it?
>
> In the previous discussion of "how to calculate fermi surface with
> VASP and WANNIER90", it seems that Jonathan said WF should be real.
> Then should the Hamilton matrix <0n|H|Rm> and the position matrix
> <0n|r|Rm> in WF basis be real accordingly? But when I print out
> hamiltonian matrix with "hr_plot = true", it's not real but complex
> with unignorable imaginary part. Is it wrong or not?
>
> Thanks in advance!
>
> Liping Chen
> Department of Chemistry
> University of Rochester
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