[CP2K:2004] Re: timestep for REAL_TIME_PROPAGATION

Hanning Chen chenh... at gmail.com
Mon Apr 20 17:33:42 UTC 2009

  I tried the new RT_PROPAGATION feature on both water and metal cluster
systems. By checking the energy conservation along with other properties, it
seems that the new feature works pretty well.

  I have another question. Does CP2k allow user to perturb the wave function
at the beginning of a real time propagation? By enabling this feature, the
evolution of a system after an ultra-short-time electric pulse being applied
can be studied, and many important physical properties, such as
photoabsorption spectrum and dynamic polarizability, can be obtained.
Theoretically, the idea is quite simple as shown below:

 Given a wave function psi(t) at time t, the wave function after the
ultra-short-time electric field perturbation psi_new(t) can be expressed as
  psi_new(t) = exp( i * K * r)   *  psi(t), where K is the electric field
strength, and r is the direction of the field. Thereafter, the system
evolves as usual.

  I do not know if CP2k developers have a plan for this feature, or I will
be happy to contribute with the developer's help.


Hanning Chen

Department of Chemistry
Northwestern University
Evanston, IL 60208

On Sat, Apr 18, 2009 at 6:20 AM, Juerg Hutter <hut... at pci.uzh.ch> wrote:

> > Dear CP2k users,
> >  I am learning to run an electron dynamics calculation with fixed nuclei
> > position. In the input file, I guess the Section
> there
> > any way to specify a time step for the wave function propagation, or the
> > time step is automatically determined by the variable %EXP_ACCURACY%?
> >
> Hi
> The timestep is set in MOTION%MD%TIMESTEP
> See also the inputs in the regression testing directory
> cp2k/tests/QS/regtest-rtp
> regards
> Juerg Hutter
> PS: This is a very new feature, carefully test your runs and we would be
> happy to get feedback.
> >  Thanks.
> >
> > Hanning Chen
> >
> > Department of Chemistry
> > Northwestern University
> > Evanston, IL 60208
> >
> > >
> >
> >
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