Subject: CCL: UV spectrum calculation (new question)

From: "Mark Thompson" <mark(at)planaria-software.com>
Date: Wed, 28 May 2003 07:53:51 -0700

Dear Serge,

> Are there any problems with numerical instabilities with the
> implemented RPA scheme in a INDO/S-RPA calculation ?

There may be, but to date, we've not had any problems running INDO/S-RPA
(aka ZINDO-RPA) on all test systems that we use for standard ZINDO.

An exhaustive reparameterization of ZINDO for RPA is not finished.  For that
matter, an exhaustive parameterization of ZINDO-CIS was also never done, but
Mike Zerner and his students over the years managed to generate a fairly
useful set of parameters for CIS that do well in most cases.  For molecules,
like cyclophanes, where low-lying double excitations may be important, then
one needs to go beyond CIS with ZINDO.  The error for ZINDO-CIS is about
1000 cm^-1 for most systems.

ZINDO-RPA appears to descibe excitations better, and generally requires a
smaller number of active orbitals in the RPA, relative to CIS.

Mark

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Mark Thompson, Ph.D.
Planaria Software
PO Box 55207
Seattle, WA  98155
FAX: 206-440-3305

ArgusLab 3.1 is available at:
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