Subject: Re: CCL:fractional nuclear charge

From: Rene Fournier - 1999-07-07 <renef!at!yorku.ca>
Date: Thu, 6 Nov 2003 10:17:03 -0500 (EST)

Hello Steve, Mikael, Everyone:

As Mikael wrote, with fractional nuclear charges...

>The basis set might be a problem, as they are optimised for specific
>atoms.

   I totally agree.

>I guess one way of getting around this would be to use a combined
>basis set for the metamorphosing atom, consisting of the BS of both
>the initial (O) and the final (N) atoms.

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".

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. 

-- Rene
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|   Rene Fournier, Associate Professor   |
|   Chemistry Dpt, York University       |
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