CCL: Diffuse functions

Title: Re: CCL: Diffuse functions
Hi, thanks. Yes I tried that and the orbitals on the donor side got a little bigger. I guess I was looking for a general conclusion about diffuse functions. In my experience, the general conclusions and shape of orbitals is rather basis set independent and I was hoping for someone to confirm that for me. Do you know if this is indeed true?

Hard to find such things in the literature. If anyone has a reference that would be great.

Best Regards,

Peter


On 4/14/11 3:31 PM, "Abrash, Sam sabrash(0)richmond.edu" <owner-chemistry^-^ccl.net> wrote:

What method did you use to determine the LUMO?  If you only used a ground state method to describe the virtual orbitals (the lowest energy of which is the LUMO), then the LUMO description is almost certainly incorrect.  Try using TDDFT rather than a ground state method.
 
In addition to determine whether the difference in your results is due to the finite field method or the basis set, rerun your DFT results using the diffuse basis set and compare the results.
 
Good luck!
 
Sam
 
Samuel A. Abrash
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From: owner-chemistry+sabrash==richmond.edu^-^ccl.net [mailto:owner-chemistry+sabrash==richmond.edu^-^ccl.net] On Behalf Of P.D.Jarowski{:}surrey.ac.uk
Sent: Thursday, April 14, 2011 4:53 AM
To: Abrash, Sam
Subject: CCL: Diffuse functions
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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