[Pw_forum] questions about some parameter in cp.x
giannozz at nest.sns.it
Tue Mar 11 13:31:04 CET 2008
hyello25 Qgrui wrote:
> (1) ion_nstep
"ion_nstepe". Used only for dynamics on the Born-Oppenheimer surface,
i.e. with electrons on the ground state. It is not used for the
Car-Parrinello dynamics. I am not even sure it is really used
> As mentioned in the Doc/input_CP, fnosep means the oscillation freq.
> of the nose thermostat. While in the Doc/INPUT.HOWTO, I was told
> QNP=2*g*Kb/Omega^2, where Omega is the typical ionic frequency. Dose
> fnosep and Omega represent the same thing?
you are answering your own question: no.
> If a system was calculated with the phonon frequency at Gamma point,
> such as 100cm^-1, 200cm^-1, 500cm^-1 respective, How should I set the
> fnosep? is fnosep=7.5 ok, because of 3 THz=100cm^-1 and Omega should be
> half of the maximum phonon freq?
the best way to know is to try
> In the SYSTEM namelist,
> (3)ecfixed, qcutz, q2sigma
> What is the general value we often use in vc-MD process? I think
> this question is stupid, these parameters value may come from
> experience. While how can I know, the value I set is ok or bad?
some explanation here:
Paolo Giannozzi, Democritos and University of Udine, Italy
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