[Pw_forum] nondegenerate electrons in DFT.

[Jiayu Dai]

So, is there the part of xc functional at finite temperature in QE code? 
I want to check the influence of the temperature-dependent xc functional at very
high temperature. If there is not the one, i think we should change this part in
the code.

Furthermore, i think DFT can deal with the system when T/T_F is close to 1, but it
should be failed when T/T_F is much greater than 1. Is it right?

Thanks very much!



>
>Jiayu Dai wrote:
> >
> > Recently, i was dealing with systems with nondegenerate electrons, that is,
when
> > T/T_F > 1 (T_F is the fermi temperature). I read some papers, and somebody
said
> > that the calculation for these system is prohibitive in DFT. I did not know
why
> > they said so. As my understanding, there is no limit in DFT to do with these
> > system. Although electrons are fermi particles, but the fermi distribution
promise
> > the right states of electrons in the calculations.  And i did not find any
> > explanation about this in the textbook of DFT in my hand.
> >
> > As an example, when the temperature is high enough, so that T/T_F is greater
than
> > 1, we can increase the bands window to deal with these cases, i think. Is it
> > correct for my understanding? 
> >
> > Thanks a lot.
> >
> > Jiayu
> >   
> 
> Correct - you would use Fermi-Dirac for the electronic occupations, and 
> include
> enough bands to make sure the the highest bands are almost empty.
> 
> This is the canonical extension to DFT according to Mermin (look at his 
> Phys Rev papers
> from the late 60s) - note that the true xc functional would be 
> temperature-dependent, but
> you would use a 0 temperature one. There might be early work (Singwi ?) 
> on the matter.
> 
>                 nicola
> 
> 
> -- 
> ---------------------------------------------------------------------
> Prof Nicola Marzari   Department of Materials Science and Engineering
> 13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
> tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu 
> 
> 




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Jiayu Dai
Department of Physics
National University of Defense Technology, 
Changsha, 410073, P R China
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