[Pw_forum] pair correlation function and the choice of fnosep (fwd)

[Antonio Tilocca]

Dear Bertrand:

> Dear Users,
> I have two preccupations:
> 1) The first one is on how to calculate the pair-correlation functions
> from CP.x output?

you will need a simple code to post-process the atomic coordinates taken
from the cp.pos trajectory file. Have a look for instance at the routines
in the Allen-Tildesley book.


> 2) The second is the following: when sampling the canonical ensemble in
> cp.x we should choice the parameter "fnosep". In all texts related to
> QE, it is written that fnosep "should be chosen to be comparable with the
> center of the vibrational spectrum of the system".
> My question is: Does it means that we have first to compute the phonon
> spectrum of the system? or what to do?

you do not need to calculate the phonon spectrum: you could pick fnosep
based on experimental vibrational data, if available, for your system, or based on
some general knowledge about its characteristic vibrational modes.

Antonio Tilocca
Chemistry - UCL



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Date: Tue, 27 Oct 2009 15:49:13 +0000 (GMT)
From: Bertrand SITAMTZE <siyouber at yahoo.fr>
Subject: [Pw_forum] pair correlation function and  the choice of