The ABINIT Users Mailing List ( CLOSED )

[vikas sharma <vikassharma_jnu@yahoo.co.in>]

Hello,
I am planing to buy a new system to perform the calculations using abins or abinip package. Being a beginner in the software knowledge I am unable to generate the binaries therefore planing to buy 64 bit amd processor (opteron) as I see the already compiled available binaries for amd+linux+gfortran+openmpi.
 I will be obliged if someone can tell the specific useful opteron model number with the combinatin of linux version + procesor + compiler + libraries for a successful run.
 Recently I tried it on linux-ubuntu-8.04+gfortran 4.3.2 on opteron 2222.
thanks in advance

Vikas Sharma,
Research Scholar,
Physics Department,
IIT Delhi, New Delhi-16, India.


--- On Mon, 2/2/09, matthieu verstraete <matthieu.jean.verstraete@gmail.com> wrote:

From: matthieu verstraete <matthieu.jean.verstraete@gmail.com>
Subject: [abinit-forum] Free Energy equation
To: forum@abinit.org
Date: Monday, 2 February, 2009, 6:19 PM

Hello everyone,

I have recently found in a paper a formula for calculating the Free energy from the phonon frequencies:

int_w g(w) (w/2 + T log (1 - exp(-w/T)))

cited as Cochrane and Cowley "Handbook der Physik" Springer (1967) - it looks like the 2002 version no longer has this formula... According to PRL 100 095901 this should be more precise (higher order) for anharmonic contributions...

The equation is quite different from that implemented in abinit (from PRB 51 8610):

int_w g(w) log ( 2 sinh (w/2T) )

The resulting 0 point energy is the same, but the higher energy (even just w > 30 cm-1 in the integrand) behavior is very different. For 300K I get a factor of 2 difference between the formulae.

Does anyone know which of these (or other equations for F) is better, or more general? Or which relation there exists between the two? Which cases justify using one or the other?

Cheers,

Matthieu

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

European Theoretical Spectroscopy Facility (ETSF) 
Dpto. Fisica de Materiales, 
U. del Pais Vasco,            
Centro Joxe Mari Korta, Av. de Tolosa, 72,   Phone: +34-943018393
E-20018 Donostia-San Sebastian, Spain        Fax  : +34-943018390

Mail : matthieu.jean.verstraete@gmail.com
http://www-users.york.ac.uk/~mjv500

---

 Add more friends to your messenger and enjoy!  Invite them now.