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Dear Professor Marzari,<br>
<br>
Thank you so much for your reply.<br>
The references you suggested to me are very helpful.<br>
Best,<br>
<br>
Eric.<br>
<br>
On 02/05/2011 08:31 AM, Nicola Marzari wrote:
<blockquote cite="mid:4D4D512F.7090207@materials.ox.ac.uk"
type="cite">On 2/5/11 3:04 PM, Eric Germaneau wrote:
<br>
<blockquote type="cite">Dear all,
<br>
<br>
I'm new in using DFT codes and especially pwscf.
<br>
I'd like to calculate the Gibbs free energy of a crystal as
function of
<br>
temperature in order to study it's stability.
<br>
How would you proceed?
<br>
I thank you in advance,
<br>
<br>
Eric.
<br>
<br>
</blockquote>
<br>
<br>
Hi Eric,
<br>
<br>
Gibbs is E+PV-TS - the enthalpy term is easy (pwscf deals e.g.
<br>
with constant pressure calculations, or you could just calculate
the
<br>
equation of state and from that the enthalpy), and for the entropy
<br>
the most relevant part is the vibrational entropy, that you could
<br>
e.g. calculate in the harmonic or quasiharmonic approximations.
<br>
<br>
Have a look at e.g. the papers of Dario Alfe and Mike Gillan
<br>
(~1998-2005) - some of them deal with the more complex problem of
calculating the free energies of liquid and solid iron, but I
<br>
believe there was one dealing just with solid-solid
transformations.
<br>
<br>
A brief tutorial on quasiharmonic is also in our PRB 71, 205214
(2005)
<br>
<br>
Best,
<br>
<br>
nicola
<br>
<br>
</blockquote>
<br>
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<br>
<a href="mailto:germaneau@gucas.ac.cn">Dr. Éric Germaneau</a><br>
<br>
College of Physical Sciences<br>
Graduate University of ChineseAcademy of Sciences<br>
Yuquan Road 19A<br>
Beijing 100049<br>
China<br>
<br>
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