---------- Forwarded message ---------- From: Stefano Baroni <bar...@sissa.it> Date: Tue, Aug 23, 2011 at 12:15 PM Subject: Re: [Pw_forum] phonon instability To: PWSCF Forum <pw_forum at pwscf.org>
On Aug 23, 2011, at 8:40 PM, bhabya sahoo wrote: sir ??? i am calculating the phase transition of some carbides the transition from B1 to B2 transition occures at 130 gpa by enthalpy compparison OK but i am able to find phonon instability at 130 gpa for B1 structure you mean, a phonon (which mode?) goes soft at the same pressure at which the enthalpies of the two phase coincide? TA branch in the gamma -X-R directions for B1 phase - but at the same time i am not able to find the dyanamic stability of B2 phase at 130 gpa ??? but it occures high pressure (more than130 gpa ) ??? is there any explanation for this ? explanation for WHAT? why the phonon instability occures at 130 gpa for B2 strcuture in the gamma -x directions for B2 structure although it is thermodyanamical stable by enthalpy comparison what are you talking about? may we expect a somewhat more well thought and articulate question? is there any relation of thermodyanamical unstability and dyanamical unstability simultaneously? ??? answers are highly appriceted with some reson well-thought and well documented questions questions would be even more appreciAted for any reAson ... SB --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110823/010bd5a4/attachment.htm