[Pw_forum] confusion in ev.x

[Paolo Giannozzi]

On Aug 21, 2012, at 16:39 , karan deep wrote:

> Birch function used in this program is P(V) equation and  for   
> istate=1 i.e birch 1st order
> is actually a 3rd order Birch-Murnaghan equation of  state as  
> mentioned in WIKIPEDIA
> page


I took the so-called "Birch 1st and 2nd order" and "Keane" equations  
of state
from some geophysics paper many years ago. Nobody has ever complained
since (which doesn't mean much about their correctness, tough). I cannot
check those papers now because I am away from my desk. Clearly these
formulae do not look like those of Wikipedia, but I am not sure how many
variants of Birch-Murnaghan equations of states exist, and how  
reliable is
Wikipedia on this subject. People working in geophysics are kindly  
requested
to comment

P.
---
Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222