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
Department of Chemistry
University of
Richmond
Richmond, VA 23173
Phone:Â 804-289-8248
Fax:Â
804-287-1897
E-mail:Â sabrash ^%at%^
richmond.edu
Web-page:Â http://www.richmond.edu/~sabrash
"In
1893 Charles Hinton left Japan to become a mathematics instructor at
Princeton University, where he invented a baseball-pitching machine that
used gunpowder to propel the balls, like a cannon. After several
accidents, the device was abandoned and Hinton lost his job ..." Terry
Pratchett, Ian Steward and Jack Cohen, The Science of Diskworld
III
From:
owner-chemistry+sabrash==richmond.edu ^%at%^ ccl.net
[mailto:owner-chemistry+sabrash==richmond.edu ^%at%^ 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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