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