[Pw_forum] question about nose-hoover thermostat-PWscf

[Veronica Muriel Sanchez]

Hi Kostya,

Thanks for your response, it was very helpful.

Veronica

El lun, 07-04-2008 a las 13:30 -0700, Konstantin Kudin escribió:
> Hi Veronica,
> 
>  The CP code only requires the frequency of the thermostat in THz, and
> Doc/INPUT.HOWTO is not applicable in this case.
> 
>  As a rough guidance, 3 terahertz = 100 cm^-1 .
> 
>  So, suppose you are simulating heavy water where low frequencies are
> around 200 cm^-1, and high frequencies near 2500 cm^-1. Then thermostat
> frequency could be around 800 cm^-1, resulting in "fnosep=24.0" for the
> CP code.
> 
>  You could also use chains, and make frequencies in the chain vary.
> Then you can set:
> nhpcl = 4
> fnosep = 12.0 9.0 6.0 3.0
> and you'll have a chain of thermostats with 400, 300, 200, 100 cm^-1.
> 
>  I hope this helps a bit.
> 
>  Kostya
>  
> 
>  Kostya
> 
> --- Veronica  Muriel Sanchez <vero at qi.fcen.uba.ar> wrote:
> 
> > Hello,
> > 
> > My name is Veronica Sanchez, I'm doing my PhD study on material
> > science.
> > I want to perform a dynamic calculation using the Nose-Hoover
> > thermostat
> > implemented in the Quantum Espresso code, using a Car-Parinello
> > dynamic.
> > 
> > I read your question (and the answer) in the PWscf forum. I have the
> > same question as you did. You wrote this:
> > 
> > 
> >  "(2) fnosep
> >     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?"
> > 
> > I know from the answer that is not the same, but I still don't know
> > how to determine the fnosep parameter.
> > If you have understood how to do it, I will be very greatful if you
> > can help me.
> > 
> > Thanks in advanced,
> > Best regards,
> > 
> > Verónica Sánchez
> > 
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> > 
> 
> 
> 
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