<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear Lily,<div><br></div><div>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. </div><div><br></div><div>HTH - SB</div><div><br><div><div>On Dec 6, 2011, at 9:24 AM, Lily Anh wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div>Hi all,</div><div><br></div><div>Is it possible to observe the <span class="Apple-style-span" style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 21px; "> </span><span class="Apple-style-span" style="color: rgb(51, 51, 51); font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 21px; ">spontaneous</span> 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?</div><div><br></div><div>Any discussion is helpful！</div><div><br></div><div>Regards & Thank you</div><div>Lily</div></div></div>_______________________________________________<br>Pw_forum mailing list<br><a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>http://www.democritos.it/mailman/listinfo/pw_forum<br></blockquote></div><br><div>
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