[Pw_forum] question about nose-hoover thermostat-PWscf

[Axel Kohlmeyer]

On Mon, 7 Apr 2008, Veronica  Muriel Sanchez wrote:

hi veronica,

please let me commend you for giving an almost perfect
example of how a question should be asked on a user forum.

- you introduce yourself and the nature of the system that
  you want to investigate
- you have read the documentation and researched the mailing
  list archives
- you clearly describe your problem and in that also give a hint
  how the documentation can be improved
- you give feedback on whether the answer was useful.

to see this every once in a while is very motivating.

congratulations and thanks,
    axel.


VMS> Hi Kostya,
VMS> 
VMS> Thanks for your response, it was very helpful.
VMS> 
VMS> Veronica
VMS> 
VMS> El lun, 07-04-2008 a las 13:30 -0700, Konstantin Kudin escribió:
VMS> > Hi Veronica,
VMS> > 
VMS> >  The CP code only requires the frequency of the thermostat in THz, and
VMS> > Doc/INPUT.HOWTO is not applicable in this case.
VMS> > 
VMS> >  As a rough guidance, 3 terahertz = 100 cm^-1 .
VMS> > 
VMS> >  So, suppose you are simulating heavy water where low frequencies are
VMS> > around 200 cm^-1, and high frequencies near 2500 cm^-1. Then thermostat
VMS> > frequency could be around 800 cm^-1, resulting in "fnosep=24.0" for the
VMS> > CP code.
VMS> > 
VMS> >  You could also use chains, and make frequencies in the chain vary.
VMS> > Then you can set:
VMS> > nhpcl = 4
VMS> > fnosep = 12.0 9.0 6.0 3.0
VMS> > and you'll have a chain of thermostats with 400, 300, 200, 100 cm^-1.
VMS> > 
VMS> >  I hope this helps a bit.
VMS> > 
VMS> >  Kostya
VMS> >  
VMS> > 
VMS> >  Kostya
VMS> > 
VMS> > --- Veronica  Muriel Sanchez <vero at qi.fcen.uba.ar> wrote:
VMS> > 
VMS> > > Hello,
VMS> > > 
VMS> > > My name is Veronica Sanchez, I'm doing my PhD study on material
VMS> > > science.
VMS> > > I want to perform a dynamic calculation using the Nose-Hoover
VMS> > > thermostat
VMS> > > implemented in the Quantum Espresso code, using a Car-Parinello
VMS> > > dynamic.
VMS> > > 
VMS> > > I read your question (and the answer) in the PWscf forum. I have the
VMS> > > same question as you did. You wrote this:
VMS> > > 
VMS> > > 
VMS> > >  "(2) fnosep
VMS> > >     As mentioned in the Doc/input_CP, fnosep means the oscillation
VMS> > > freq. of
VMS> > > the nose thermostat. While in the Doc/INPUT.HOWTO, I was told
VMS> > > QNP=2*g*Kb/Omega^2, where Omega is the typical ionic frequency. Dose
VMS> > > fnosep
VMS> > > and Omega represent the same thing?"
VMS> > > 
VMS> > > I know from the answer that is not the same, but I still don't know
VMS> > > how to determine the fnosep parameter.
VMS> > > If you have understood how to do it, I will be very greatful if you
VMS> > > can help me.
VMS> > > 
VMS> > > Thanks in advanced,
VMS> > > Best regards,
VMS> > > 
VMS> > > Verónica Sánchez
VMS> > > 
VMS> > > _______________________________________________
VMS> > > Pw_forum mailing list
VMS> > > Pw_forum at pwscf.org
VMS> > > http://www.democritos.it/mailman/listinfo/pw_forum
VMS> > > 
VMS> > 
VMS> > 
VMS> > 
VMS> >       ____________________________________________________________________________________
VMS> > You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access, No Cost.  
VMS> > http://tc.deals.yahoo.com/tc/blockbuster/text5.com
VMS> > _______________________________________________
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VMS> > Pw_forum at pwscf.org
VMS> > http://www.democritos.it/mailman/listinfo/pw_forum
VMS> > 
VMS> 
VMS> _______________________________________________
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VMS> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.