Subject: Absorption spectra from ZINDO/S

From: "Eugene G. Noda" <[email-masked]>
Date: Mon, 13 Oct 1997 19:28:07 +0300

Dear CCLers

       We try to calculate the UV-VIS absorption spectra of some orgnic
compounds
such as 5,12- and 5,11-naphthacenequinones by ZINDO/S semiempirical method.
Geometry optimization of these molecules was obtained using the AM1 method (as
in paper Chem.Phys.Lett. 250 (1996) 31-39). We use HYPERCHEM 4.5 program
package. If you are interesded in detailed chemical formula of compounds
that are
actual for our applications we may send them to you separately.
       However the calculated values of exited level energy are incorrect.
Moreover
the results of energy calculations for simple molecules taken as an example
(like
benzene, naphthalene and others) are also incorrect. We find that in
Semi-empirical
Options Dialog Box (Setup Menu) for ZINDO/S method there are the Overlap
Weighting Factors, which can be manually modified in the region 0-2. Default
values of sigma-sigma parameter is 1,267 and pi-pi parameter is 0,64.

So the questions is:

1.   Whether we can change these parameters to calculate the correct absorption
spectra and how the values of these parameters ought to be estimated?

And in addition:

2.   What are the best to your knowledge program packs (semi- or ab initio),
which allow
reasonable calculation of solid state optical properties (nonlinearity,
propagation, etc.)?

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From: satyam <[email-masked]>
Date: Mon, 13 Oct 1997 16:50:16 -0400 (EDT)

Dear Eugene,

HyperChem or any other packages will give right results if 
one inputs the right parameters. Hence it is important that
one reads the theoretical background behind all those boxes
given in the softwares, in your case, Overlap Weighting Factors.

ZINDO/S is INDO/S method developed by Zerner and coworkers.
Zerner's review in 

Reviews in Computational Chemistry Vol. 2 (1991) pages 313

gives the value of pi-pi interaction as 0.585 as universal parameter.

It points to all relevant literature. 

The value of 0.64 comes from calculations based upon metal complexes.
(see papers of Tom Cundari, Zerner and Larsson).

Please look at this reviews and references therein.

Satyam

_________________________________________________________________________

    DNA: Insulator or Wire ?  C&EN February 24, 1997
_________________________________________________________________________
Dr. Satyam Priyadarshy                
Research Assitant Professor           Department of Chemistry
University of Pittsburgh              Pittsburgh, PA 15260
Phone: 412-624-8200 Extn 8589         Fax: 412-624-8589
Email: [email-masked]        [email-masked]
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On Mon, 13 Oct 1997, Eugene G. Noda wrote:

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             -----------------------------------------------------
                            Dr. Satyam Priyadarshy
                    107D, Chevron, Department of Chemistry
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