[Wien] NaCl Phonon calculations

[Chandrika]

Hi Sergio,
First your unit cell must be optimised (with mini or vol opt) for small 
forces. Then in the run_phonon_lapw you need to converge the forces to about 
0.004 Ry (if you have the latest Phonon).
Best of luck,
Chandrika
----- Original Message ----- 
From: "Sergio Yanuen Rodriguez" <srodriguez at physics.tamu.edu>
To: <wien at zeus.theochem.tuwien.ac.at>
Sent: Friday, February 22, 2008 4:10 AM
Subject: [Wien] NaCl Phonon calculations


> Dear Wien2k users
>
> I am trying to do phonon calculations for NaCl because this system is
> already studied and after this apply this method to something more
> complicated, I generate the case.d45 with PHONON for a 2X2X2 supercell,
> then I transfer this file to Wien 2k and calculate the forces, but when I
> run analyse_phonon the sum of this forces are not small, and the results I
> get do not seem alright. I compared this results with another ones and
> they do not agree specially for the acoustic modes. Since I am getting
> negative frequencies at Gamma where they must have 3 (nearly) zero
> frequencies.
>
> Does any one know which parameter is important to adjust to make the sum
> of the forces small? or do I have to do a volume optimization before
> calculating the forces? Or any suggestions
>
> I really appreciate any help.
>
> Sergio Y. Rodriguez
> Physics Department
> Texas A&M University
>
>
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