[Wien] phonon calculation

[Ghosh SUDDHASATTWA]

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
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