[CPMD-list] question on thermal energy tranfer

[Axel Kohlmeyer]

On Sat, 7 Apr 2007, Tengfei Luo wrote:

TL> Dear Axel:
TL> 
TL> Thank you for your analysis and suggestion. Where can I find the fourier.x 
TL> code? I did some search online, but I couldn't find it anywhere.

check out the contrib section in the www.cpmd.org download area.

a.

TL> 
TL> Thank you again!
TL> 
TL> Tengfei
TL> 
TL> ----- Original Message ----- 
TL> From: "Axel Kohlmeyer" <akohlmey at cmm.chem.upenn.edu>
TL> To: "Tengfei Luo" <luotengf at msu.edu>
TL> Cc: <cpmd-list at cpmd.org>
TL> Sent: Saturday, April 07, 2007 2:54 PM
TL> Subject: Re: [CPMD-list] question on thermal energy tranfer
TL> 
TL> 
TL> > On Sat, 7 Apr 2007, Tengfei Luo wrote:
TL> >
TL> > TL> Dear All:
TL> >
TL> > TL> I have some question on the result of thermal energy equilibration.
TL> > TL> Experts, could you please look at my inputs to see if there is
TL> > TL> anything wrong?
TL> >
TL> > [...]
TL> >
TL> > TL> But I got a result very strange: the temperature of the two
TL> > TL> materials doesn't go a uniform temperature after the thermostates
TL> > TL> are erased no matter how many steps I run. I cannot explain this
TL> > TL> phenomena physically. Why the temperatures don't go to a same
TL> > TL> temperature, but there is indeed a little temperature drop of high
TL> > TL> temperature side and a little raise in the low temperature side.
TL> >
TL> > have you considered that - due to different atomic masses - bulk
TL> > Si and bulk Ge have different characteristic frequencies and that
TL> > there can be very little overlap of the phonon spectra? even more
TL> > so since are running at very low temperature 50/100K so that only
TL> > low lying phononic states would be excited.
TL> >
TL> > TL> BTW, When I used silicon in both group and germanium in both group,
TL> > TL> the temperature get to a uniform temperature after some thoudands of
TL> > TL> steps. (I wrote a little code to process the trajectory file to
TL> > TL> evaluate the temperature of each part.)
TL> >
TL> > i suggest, you run the velocities from your trajectories (for each
TL> > atom individually and then averaged over groups) through the fourier.x
TL> > code to look at the vibrational spectral densities. bob williams
TL> > has contributed some code to the package for that purpose.
TL> >
TL> > cheers,
TL> >   axel.
TL> >
TL> > TL> I would like to provide any further information if it's needed!
TL> > TL>
TL> > TL> Thank you in advance!
TL> > TL>
TL> > TL> Tengfei
TL> >
TL> > -- 
TL> > =======================================================================
TL> > Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
TL> >   Center for Molecular Modeling   --   University of Pennsylvania
TL> > Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
TL> > tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
TL> > =======================================================================
TL> > If you make something idiot-proof, the universe creates a better idiot.
TL> >
TL> > 
TL> 

-- 
=======================================================================
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
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.