Subject: Re: CCL:DFT: local / non-local

From: Juan Carlos Sancho <[email-masked]>
Date: Wed, 18 Nov 1998 14:59:47 +0100

> 
> Hi.
> 
> two questions concerning DFT functionals:
> 
> 1) what are the *exact* definitions of local vs. non-local?
>

This is an critical point in DFT. Nowadays, there is a great interest in
properties of the exchange and correlation functionals like homogeneity
and locality. From the DFT point of view, a functional is local when all
the terms in the functional derivative, with the exception of the first,
vanish. What does it means?. It can be presumed that we are dealing with
non-local functionals, so we can suppose several non-local dependences
(succesive derivatives of the density) in the exchange or correlation
integrand. From here, the corresponding contribution to the functional
derivative is obtained. The complete corrections to the first, local
term, would reproduce the exact potential if DFT is exact.

>
> 2) is the LYP correlation functional, which incorporates gradient
> corrections, local or non-local?
>

Following the previous discussion:non-local, since it will provide
higher order corrections to the local term in the correlation potential.

Juan Carlos

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