[Pw_forum] study the phase transition with vc-md or vc-cp

[Stefano Baroni]

Dear Lily,

the answer, as it often is, is "it depends". Different crystal structures are usually separated by an enthalpy barrier, whose crossing is a "rare event" if its height is sufficiently high.  In order to observe the transition in an actual MD run, you have to either overheat or overload the system, or to bias the dynamics using one of the many available techniques, the most powerful and popular one probably being metadyamics. I am no expert in this field, but I think that the problem has been extensively treated in the literature. References that naturally occur to me are the original paper by Parrinello and Raman, or the more recent one by Parrinello and Laio on metadynamics (as well as others coauthored by R. Martonak, specifically on crystal-structure sampling), as well as the literature citing these articles. 

HTH - SB

On Dec 6, 2011, at 9:24 AM, Lily Anh wrote:

> Hi all,
> 
> Is it possible to observe the  spontaneous phase transitions by the vc-md (PW.X) or vc-cp (CP.X) simulations staring from the initial structure input? If possible, what should we do?
> 
> Any discussion is  helpful！
> 
> Regards & Thank you
> Lily
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---
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 pensée - Jean Piaget

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