[Wien] phonon calculation

[Yundi Quan]

Dear Ghosh,
Thanks for you explanation. Now I got it.
I have another problem. After running  'min ....', I got a structure with
very small force. However, when I do another calculation with the structure
I got, the total force on each atom becomes very large. What is the reason
for this?


Yundi

On Mon, Sep 26, 2011 at 7:44 PM, Ghosh SUDDHASATTWA <ssghosh at igcar.gov.in>wrote:

> Dear Yundi,
> If I understand your question correctly, then just by doing step 1, you
> cannot get energy minimum but by doing the following
> 1. Optimize lattice parameters
> 2. use optimized lattice parameters and then min_lapw
> 3. Use optimized lattice parameters and optimized atomic positions and get
> ENE (including -so or any other options)
>
> Only after step 3, can you say that you have energy minimum.
>
> -----Original Message-----
> From: wien-bounces at zeus.theochem.tuwien.ac.at
> [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Yundi Quan
> Sent: Monday, September 26, 2011 9:25 PM
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] phonon calculation
>
> In the second step, what if the total energy changes with the internal
> structure so that the so-called energy minimum found in step one is no
> longer a energy minimum?
>
> Yundi
>
> 2011/9/26 Ghosh SUDDHASATTWA <ssghosh at igcar.gov.in>:
> > Dear Yundi,
> > What I follow is
> > 1. do volume or c/a, b/a relaxation depending on your structure
> > 2. Use the optimized lattice parameters to do min_lapw
> > 3. Use the optimized lattice parameters and atomic positions to define
> the
> > supercell in Phonon software
> > 4. import the d45 file from phonon to wien2k
> > 5. run phonon.job in wien2k
> > 6. get the force file and export it to phonon
> > 7. get the phonon dispersion
> >
> > you can use -fc 1.0 in min_lapw as well as in phonon. you can then try
> -fc
> > 0.50 and then so on
> >
> > SG
> >
> > ________________________________
> > From: wien-bounces at zeus.theochem.tuwien.ac.at
> > [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Yundi Quan
> > Sent: Monday, September 26, 2011 3:41 PM
> > To: A Mailing list for WIEN2k users
> > Subject: [Wien] phonon calculation
> >
> > In order to get the correct input structure for phonon calculation, I
> need
> > to first find the structure with minimal force. How much force is small
> > enough? Is 1.0 mRy/bohr small enough? (I only want to calculate the
> phonon
> > at gamma point to see whether the system is stable or not at gamma point)
> > Should I first carry out internal structure minimization or crystal
> > structure minimization?
> >
> >
> > Yundi
> > _______________________________________________
> > Wien mailing list
> > Wien at zeus.theochem.tuwien.ac.at
> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >
> >
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20110926/3552a3bb/attachment.htm>