somewhere in time

下面是昨天给一个暑期学校同学回的邮件的主体部分。 

As you know, “Fermi level” is the term used to describe the top of the collection of electron energy levels at absolute zero temperature. This concept comes from Fermi-Dirac statistics. Electrons are fermions and by the Pauli exclusion principle cannot exist in identical energy states. So at absolute zero they pack into the lowest available energy states and build up a “Fermi sea” of electron energy states. The Fermi level is the level at which the electron occupancy is 0.5 (or the highest filled level at 0 K).

So it is at the equal foot of your define. And at the other temperature, the $E_f=(E_{HOMO}+E_{LUMO})/2$. Relatively, at the 0K, the eletrons are localized at the HOMO downwards, so the $E_f=E_{HOMO}$.

But at the real system calculations, we do really not place the Fermi Level at the middle of the HOMO and LUMO, and a experiential parameter is set to.

This entry was posted on Sunday, September 9th, 2007 at 2:35 pm and is filed under My Study. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.