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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