[Pw_forum] question about nose-hoover thermostat-PWscf

[Konstantin Kudin]

 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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