[Pw_forum] finite temperature DFT

Nicola Marzari marzari at MIT.EDU
Thu Mar 19 14:39:49 CET 2009

戴佳钰 wrote:
> Thanks for your answer, and it is very helpful. 
> So, you mean the temperature is set to be smearing_width here, all right? And if
> i
> want to perform molecule dynamics, i have to use the tempw and the method of
> thermostat at the same time? Then, the tempw and the smearing_width must be
> equal.
> And do we need to consider the chemical potential of the ensemble?
> Thanks a lot.
> Jiayu Dai
> National University of Defense Technology, P R China

Correct (re tempw). But note that unless you have high temperatures, of 
thousands of degrees, you will not see much of an effect (at all) in
what happens to the electrons.

Try it yourself, and see how much e.g. forces on atoms depend on

The chemical potential of the electrons is the fermi energy, fixed so
that you have system neutrality, or whatever you specify in nelec.

The atoms are fixed in number, so you cannot specify their chemical
potential - you would do simulations in the NVT or NPT ensemble, both
for the ions and the electrons.


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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