CCL: Diffuse functions

[<P.D.Jarowski**surrey.ac.uk>]

 Dear all,

I am
 facing a problem in the molecular orbital representation of some dipolar
 chromophores using two different methods. In the first case we have a b3lyp
 /6-31g(d) homo and lumo level where there is almost equal density on both the
 donor and acceptor portion of the molecule. In other words, the eigenstates are
 very delocalized. When using a finite field method with a 6-31++g basis the homo
 has most of the density on the donor and in the lumo its mostly on the acceptor,
 the eigenstates are more localized. 

Here is my question: could the
 implementation of the diffuse functions cause this difference?

Would a
 finite field method lead to greater localization of these
 eigenstates?

The interpretation of our experimental data will depend
 heavily on the overlap of the eigenstates.

Thanks in
 advance.

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