[Pw_forum] Can not find minimum free energy by QHA

[GAO Zhe]

Prof. Giannozzi:
Thank you very much for your kindly reply. I think this is my problem to understand Fvib.
I have also checked Axel van de Walle's Ph.D thesis, and found that free energy should be Fvib+Fconf-TSvib-TSconf. In 0GPa pressure case, Fconf should equal to total energy. Therefore I cannot obtain the right Free Energy vs Volume curve as a result of using Fvib alone.


--
GAO Zhe
CMC Lab, MSE, SNU, Seoul, S.Korea




At 2011-08-30 03:42:31,"Paolo Giannozzi" <giannozz at democritos.it> wrote:
>
>On Aug 22, 2011, at 4:36 , GAO Zhe wrote:
>
>> However, the free energy kept decreasing as a monotone decreasing
>> function of lattice parameter
>
>you mean: the "vibrational free energy" alone, or "the sum of the
>energy and of the vibrational free energy"? the vibrational free
>energy should be a small correction to the total energy.
>
>P.
>---
>Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
>Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
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