Subject: DFT, HOMO, LUMO etc

From: Eric Scerri <[email-masked]>
Date: Tue, 22 Aug 2000 01:01:46 -0800

[email-masked] writes,

>Sat, 2000 Aug 19
>
>Hello,
>
>We know that in pure DFT (in contrast to wavefunction theory) there are
>are no orbitals and there is no wavefunction; the Kohn-Sham orbitals of
>current practical DFT methods were introduced to make the calculation of
>the electron density tractable.
>
>QUESTIONS
>(1) An important feature of ab initio (and semiempirical) calculations
>is that one can visualize the orbitals, particularly the HOMO and LUMO
>(frontier orbitals) and make chemical deductions. In a _pure_ DFT
>calculation a question about the shape and energy of these orbitals
>would be meaningless, right?
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But surely the shape of the electron density which would correspond 
to these orbitals could still be visualized if necessary, just as 
electron density can be in the ab initio wavefunction approaches.

The two approaches are alternative ways of looking at the micro 
world.  Whether one chooses to visualize, or not, is always an option 
in any theory.  But perhaps you ar asking a more specific question 
like what do HOMO and LUMO electron density plots look like?

Please clarify your question (1)

eric scerri

-------------------------------------------------
Eric Scerri PhD,
Visiting Professor,
Department of Chemistry & Biochemistry,
UCLA,
Los Angeles,  CA 90095
USA

Editor of "Foundations of Chemistry"
http://www.wkap.nl/journalhome.htm/1386-4238