[Pw_forum] Wild phonons

[Paolo Giannozzi]

On Dec 19, 2007, at 15:51 , Nicola Marzari wrote:

> Note that at finite pressure one might need to be careful about
> energy and enthalpy and what is exactly that you are calculating -
> my guess is that you need the second derivatives of the enthalpy,  
> and I
> suspect that is what the phonon slopes would be, but it would be  
> better
> to check carefully the literature. Anyone care to comment ?

this is what I understood years ago when I wrote some lecture notes
mentioning this aspect: http://www.fisica.uniud.it/~giannozz/Corsi/ 
sissa02.pdf
see pages 20 and 21, and the reference quoted at the end:
PRL 78, 2493 (1993)

Paolo
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222