Thank you Prof Marzari and dear Antonio, your answers are very helpful ! many thanks
Jin 2013/4/15 Antonio Tilocca <uccaati at ucl.ac.uk> > > > > > Hi All > > > > I am a new user of cp module and I have some questions about running a > CPMD > > simulation and using cppp.x. > > > > 1. I tried to run a CPMD job with 33 water molecules in a 1*1*1 nm3 box. > > After minimizing the electrons and ions to their ground states, I started > > 'verlet' dynamics as mentioned in QE user guide, without setting tempw > > ,fnosep and ion_temperature. The tempp value (ionic temperature) directly > > went up to more than 4000 and continued increasing. Did that make sense? > > Shall I turn on temperature controlling at the same time I started verlet > > dynamics? I suppose the system should oscillate around 0K if it has been > > minimized. Or is it because I started the system with a random molecule > > distribution? > > > To answer your first question: yes, an initial "rocketing" ionic > temperature is not unexpected if you start from a configuration very far > from equilibrium, no matter how well you relax the electrons. However, > also be aware that there can be other causes for this behaviour, such as > an inappropriate (too long) time step, wrong cell vectors specified, etc. > In order to rule out the latter, you can try to start from a more stable > configuration, for instance obtained from a quick relaxation by classical > MD. In principle you could also try to turn on damped MD to prevent ions > from moving too fast and too much in the initial stages of the CP > dynamics, and > see a short damped MD run gives you a better starting configuration. > > > Antonio Tilocca > Chemistry > University College London > > > > > > > > > > > > > 2. I have defined atom species as: > > > > atomic_number(1) = 1, > > atomic_number(2) = 8, > > > > in cppp input file.However in all generated files (out/axsf/pdb) all the > > atoms are still recognized as 'H'. What should I do with that? > > > > many thanks > > > > Jin > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: > http://pwscf.org/pipermail/pw_forum/attachments/20130413/f959ea2c/attachment-0001.html > > > > ------------------------------ > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://pwscf.org/mailman/listinfo/pw_forum > > > > End of Pw_forum Digest, Vol 70, Issue 12 > > **************************************** > > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20130415/b3a4b952/attachment.html
