[Pw_forum] temperature

[Axel Kohlmeyer]

On Mon, 2009-05-25 at 00:48 -0700, ali kazempoor wrote:

dear ali,


> Dear all

> I want to study defect formation of  charged defect at required
> temperature . Since DFT is at T=0 , So I think that when we introduce

what makes you say that DFT is at T=0K???

you are using the born-oppenheimer approximation and thus you can well
study matter at elevated temperatures. however to get the properties of
matter at temperatures != 0K you have to average over all statistically
relevant configurations. please have a look into a book on statistical
mechanics.

> pressure on system it is equal to studying system at some finite 
> temperature. Is it true? and what is the relation and formula that

please provide some references or at least some rationalizations to 
back up your claims. equations of state for solids usually relate
the (potential) energy to the volume of a system (e.g. through the 
bulk modulus as a fairly constant material property). again, a look 
into a suitable textbook should help.

cheers,
   axel.

> shows how can we obtain the temperature by knowing the pressure of the
> system?


> thanks a lot
> Ali Kazempour
> Physics department, Isfahan University of Technology
> 84156 Isfahan, Iran. Tel-1: +98 311 391 3733
> Fax: +98 311 391 2376 Tel-2: +98 311 391 2375
> 
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-- 
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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
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