Subject: CCL:DFT:KS exact?

From: Steven Creve <[email-masked]>
Date: Mon, 23 Nov 1998 16:41:06 +0100 (NFT)

Hi,

in Kohn-Sham theory, the density is written as a sum over orbitals
squared. The occupation numbers of these orbitals are 1 or 0. My question:
can the density of _any_ molecular system be written in this way? Or, in
other words, are there systems where one needs fractional occupation
numbers to represent the exact density? If the answer to the latter
question is 'yes' then one might question if KS-DFT yields _in principle_
(if the exact Exc is known) the exact density.

_any_ comments are most welcome,

Steven

--------------------------------------------------------------------------
Steven Creve                       [email-masked]
Labo Quantumchemie
Celestijnenlaan 200F
3001-HEVERLEE                      tel: (32) (16) 32 73 93
BELGIUM                            fax: (32) (16) 32 79 92