[Pw_forum] gibbs free energy

[Eric Germaneau]

Dear Professor Marzari,

Thank you so much for your reply.
The references you suggested to me are very helpful.
Best,

                Eric.

On 02/05/2011 08:31 AM, Nicola Marzari wrote:
> On 2/5/11 3:04 PM, Eric Germaneau wrote:
>> Dear all,
>>
>> I'm new in using DFT codes and especially pwscf.
>> I'd like to calculate the Gibbs free energy of a crystal as function of
>> temperature in order to study it's stability.
>> How would you proceed?
>> I thank you in advance,
>>
>> Eric.
>>
>
>
> Hi Eric,
>
> Gibbs is E+PV-TS - the enthalpy term is easy (pwscf deals e.g.
> with constant pressure calculations, or you could just calculate the
> equation of state and from that the enthalpy), and for the entropy
> the most relevant part is the vibrational entropy, that you could
> e.g. calculate in the harmonic or quasiharmonic approximations.
>
> Have a look at e.g. the papers of Dario Alfe and Mike Gillan
> (~1998-2005) - some of them deal with the more complex problem of 
> calculating the free energies of liquid and solid iron, but I
> believe there was one dealing just with solid-solid transformations.
>
> A brief tutorial on quasiharmonic is also in our PRB 71, 205214 (2005)
>
> Best,
>
>             nicola
>

-- 
/Be the change you wish to see in the world
/ — Mahatma Gandhi —

Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>

College of Physical Sciences
Graduate University of ChineseAcademy of Sciences
Yuquan Road 19A
Beijing 100049
China

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