Subject: ECP's & all-electron basis

From: [email-masked] (Jirda Kozelka)
Date: Tue, 23 Apr 1996 16:48:09 +0200 (MET DST)

Hello readers,

recently, several CCL members asked about using effective core potentials 
in DFT calculations. They were advised to the recent article by Russo et al.
(J.Phys.Chem.1995,1705). In this paper, DFT calculations using HF-derived ECP's 
were compared with all-electron calculations.                                        
I do not understand one point: For both approaches, the authors utilized a 
common all-electron basis set. It is not clear to me how one can use ECP's 
together with an all-electron basis.
Since ECP calculations treat only valence electrons explicitely, the procedure
of using ECP's with an all-electron basis set looks to my simple mind like
filling valence electrons into core orbitals.
Could one of the quantum chemistry professionals show me where I am making a mistake?
Thanking you in advance,

Jirka Kozelka
[email-masked]
fax: ++331-42-86-83-87
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