Subject: Re: CCL:fractional nuclear charge

From: Mikael Johansson <mpjohans^at^pcu.helsinki.fi>
Date: Thu, 6 Nov 2003 18:52:43 +0200 (EET)

Hello Rene, Steve, and All!

On Thu, 6 Nov 2003, Rene Fournier - 1999-07-07 wrote:

> I am afraid this might give problems with near linear dependencies,
> maybe inacurrate inversion of the overlap matrix.  A way around that
> problem would be to define an "intermediate basis set" by interpolating
> two (preferably large) O and N basis sets that have the same contraction
> pattern, ie, a "metamorphosing basis set for a metamorphosing atom".

Just for fun, I tested a metamorphose of CH4 => C/NH4^{+1/2) => NH4^+,
with a combined C+N TZVP basis set for C/N. It had no convergence
problems at all, converging in 8-10 steps (PBE0 functional). Of course,
it could get more difficult with larger molecules, and a morphed basis
could be preferable.

To Steve: I suffer from imagination-malfunction today; could you please
give a hint on what information is gained from such a calculation :-)

Have a nice day,
    Mikael J.
    http://www.helsinki.fi/~mpjohans/

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From: Serguei Patchkovskii <ps^at^ned.sims.nrc.ca>
Date: Thu, 6 Nov 2003 11:16:35 -0500 (EST)

On Thu, 6 Nov 2003, Rene Fournier - 1999-07-07 wrote:
> I have a related question: does anyone know of a program that would
> allow to use positive charge distributions other than a set of point
> charges, for instance, a set of spherical Gaussian distributions.

ADF will support an arbitrary external potential, as long as you are
willing to write a routine calculating the potential at grid points.

Serguei

---
Dr. Serguei Patchkovskii

Tel: +1-(613)-990-0945
Fax: +1-(613)-947-2838
E-mail: Serguei.Patchkovskii^at^nrc.ca

Coordinator of Modelling Software
Theory and Computation Group
Steacie Institute for Molecular Sciences
National Research Council Canada
Room 2011, 100 Sussex Drive
Ottawa, Ontario
K1A 0R6 Canada