Subject: Re: Electron density at nucleus/field shift

From: "Stefan Fau" <[email-masked]>
Date: Fri, 24 Jan 2003 14:20:52 -0500

Hi Steve,

your problem IS due to using a pseudopotential.
It replaces the core electrons and therefore your
calculated electron density at the nucleus is only
the part due to valence electrons. The ECP
represents a frozen arrangement of core-electrons.
Therefore you might add a constant to your
calculated electron density to include the effect of
the core eletrons. Of course, this would not affect
the gradient w.r.t. internuclear distance.

Another possible problem are relativistic effects.
While they can usually be ignored for elements up
to Kr, they are important for heavier elements.
Relativistic effects change the mean radius of
orbitals and influence the coupling of valence
effects (like bonding) to the nuclear region.
It might therefore be a very good idea to use
a HF or DFT program that includes scalar
relativistic effects. That way, you can do
all-electron calculations including the
relativistic effects.

I know that ADF can do this, but I don't
know if it can give you the electron density
at the nuclei. Maybe other CCL members
know the answer. Maybe there are other
programs that can do this, too.

Yours,
     Stefan Fau
______________________________________________________________________
Dr. Stefan Fau                    |      [email-masked]
University of Florida             |     (352) 392-6714
Quantum Theory Project
2319 NPB #92, P.O.Box 118435
Gainesville, FL 32611-8435