Example input

[Matthias Krack]

Hi Ondrej,

it has to be done by hand, since there is no automatic procedure, yet.
You may start with a gamma like 0.001/fs and noisy_gamma=0.0/fs.
You will most likely observe a drift (drop) of the total energy.
The actual drift will mostly depend on your QS and SCF settings and
thus keep these settings fixed. Then you increase noisy_gamma until
the drift is compensated. Simultaneously, these runs may contribute
to the thermalisation of the sample. Note, this is just one possible
protocol and there might be alternative protocols to achieve the same
goal.

Matthias

On Mar 19, 10:27 am, Ondrej Marsalek <ondrej.... at gmail.com>
wrote:
> Hi again,
>
> so far, I have only tested a short run of a neat 32 water cluster and
> it blew up after about 1.5 ps. I have used
>
>         &LANGEVIN
>             GAMMA       [fs^-1] 1.0E-2
>             NOISY_GAMMA [fs^-1] 9.0E-5
>         &END LANGEVIN
>
> I will try to use a better equilibrated initial condition and tweak
> the setup. If I am not able to make it work, I'll post more details
> and some specific questions.
>
> I also have one question about the paper
>
> Thomas D. Kuhne and Matthias Krack and Michele Parrinello:
> Static and Dynamical Properties of Liquid Water from First Principles
> by a Novel Car-Parrinello-like Approach
>
> It says "... we perform a preliminary run in which we vary gamma_D on
> the fly...". Is there a way to do that in CP2K or was it done "by
> hand"?
>
> Thanks,
> Ondrej
>
> On Mon, Mar 2, 2009 at 09:51, Matthias Krack <matthia... at psi.ch> wrote:
>
> > Dear Ondrej,
>
> > you have to select the ENSEMBLE LANGEVIN together with the
> > EXTRAPOLATION ASPC (which is now the default). Activate the printing
> > of the RESTART_HISTORY to enable a smoother restart of consecutive
> > runs. Then you have to find the appropriate gamma values for your
> > system. Here is a CP2K input template showing the essential parts
> > needed for the setup:
>
> > &MOTION
> >  &MD
> >  ENSEMBLE LANGEVIN
> >  &LANGEVIN
> >   GAMMA [fs^-1] 1.0E-3 # "Langevin" gamma (adapt for your system)
> >   NOISY_GAMMA [fs^-1] 3.0E-5 # dissipative gamma (adapt for your
> > system)
> >  &END LANGEVIN
> >  ...
> >  &END MD
> > &END MOTION
>
> > &FORCE_EVAL
> >  METHOD Quickstep
> >  ...
> >  &DFT
> >  WFN_RESTART_FILE_NAME <project>-RESTART_HISTORY.wfn
> >  &QS
> >   EXTRAPOLATION ASPC
> >   EXTRAPOLATION_ORDER 3 # find the best for your system
> >   ...
> >  &END QS
> >  &SCF
> >   EPS_SCF 1.0E-7
> >   EPS_SCF_HIST 1.0E-5
> >   MAX_SCF 40
> >   #MAX_SCF_HIST 2 # instead of EPS_SCF_HIST for a fixed number of SCF
> > steps
> >   SCF_GUESS history_restart
> >   ...
> >   &OT ON
> >    MINIMIZER DIIS
> >    PRECONDITIONER FULL_KINETIC # try the cheapest first
> >    STEPSIZE 0.1
> >   &END OT
> >   &OUTER_SCF
> >    EPS_SCF 1.0E-7
> >    MAX_SCF 50
> >   &END OUTER_SCF
> >   &PRINT
> >    &RESTART_HISTORY
> >     ADD_LAST NUMERIC
> >     BACKUP_COPIES 5 # ASPC order + 2
> >     FILENAME =<project>-RESTART_HISTORY.wfn
> >     &EACH
> >      __ROOT__ 1
> >      MD 1
> >      QS_SCF 0
> >     &END EACH
> >    &END RESTART_HISTORY
> >   &END PRINT
> >   ...
> >  &END SCF
>
> > Note, the gamma values are only given to provide some reasonable
> > starting values w.r.t. their relative size and the order of magnitude.
> > You may select a fixed (very low) number of SCF iteration steps using
> > MAX_SCF_HIST or a less tight SCF convergence criterion using
> > EPS_SCF_HIST. Please, keep in mind that the procedure only pays back,
> > if you are planning long simulation runs, since setup, thermalization
> > and the adjustment of the gamma values requires already several ps of
> > simulation time.
>
> > Best regards,
>
> > Matthias
>
> > On Feb 27, 8:00 pm, Ondrej Marsalek <ondrej.... at gmail.com> wrote:
> >> Dear CP2K users,
>
> >> I am interested in the method described in this paper:
>
> >> Thomas D. Kuhne and Matthias Krack and Fawzi R. Mohamed and Michele
> >> Parrinello: Efficient and Accurate Car-Parrinello-like Approach to
> >> Born-Oppenheimer Molecular Dynamicshttp://link.aps.org/abstract/PRL/v98/e066401
>
> >> Unfortunately, I have trouble mapping the paper to a working
> >> computational setup and CP2K input. Would anyone be willing to provide
> >> an example?
>
> >> Thank you,
> >> Ondrej Marsalek
>
>