CCL: UV spectrum calculation (new question)

["Mark Thompson" <mark(at)planaria-software.com>]

 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
 =================================
 Mark Thompson, Ph.D.
 Planaria Software
 PO Box 55207
 Seattle, WA  98155
 FAX: 206-440-3305
 ArgusLab 3.1 is available at:
 http://www.arguslab.com
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