[Pw_forum] cp with metals

[Nichols A. Romero]

Nicola,

A couple of questions and comments

In example 29,

1. The example runs, but gives the message:
degauss is not use in CP

Is it ignoring the flag completely in the ensemble DFT?

2. The example does not work when emass and emass_cutoff are commented out.
Those arguments shouldn't be necessary if you are doing BO instead of CP in the
ensemble DFT.

3. Hypothetically speaking, I should be able to do BO without the
ensemble DFT in the CP code if I was dealing with an insulator. Using
the Gram-Schmidt and CG, diagonalization options.

Thanks,
On 11/23/05, Konstantin Kudin <konstantin_kudin at yahoo.com> wrote:
>  Hi all,
>
>  I'd like to point out that electronic thermostats is a pretty
> dangeorous thing to use for any production calculations unless one
> really knows what is going on there.
>
>  The main issue is that there is usually some "natural" fictitious
> kinetic energy that electrons gain from the ionic motion ("drag"). One
> could easily quantify how much of the fictitious energy comes from this
> drag by doing a CP run, then a couple of CG (same as BO) steps, and
> then going back to CP. The fictitious electronic energy at the last CP
> restart will be purely due to the drag effect.
>
>  The thermostat on electrons will either try to overexcite the
> otherwise "cold" electrons, or, will try to take them down to an
> unnaturally cold state where their fictitious kinetic energy is even
> below what would be just due pure drag. Neither of this is good.
>
>  I think the only workable regime with an electronic thermostat is a
> mild overexcitation of the electrons, however, to do this one will need
> to know rather precisely what is the fictititious kinetic energy due to
> the drag.
>
>  Kostya
>
>
> --- Davide Ceresoli <ceresoli at sissa.it> wrote:
>
> > Nichols A. Romero wrote:
> > > Hi,
> > >
> > > How does the Car-Parinello MD code in the ESPRESSO package handle
> > > metallic cases? Does it implement the method by Blochl et. al PRB
> > 45,
> > > 9413 (1992).
> > >
> > Yes, in namelist &electrons:
> >      electron_temperature = 'nose' or 'rescaling'
> >
> > Best,
> >      Davide
>
>
>
>
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--
Dr. Nichols A. Romero, PhD.
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