[molpro-user] CASPT2 / RS2 Excited State Calculation

[Joseph Lane]

Good morning,

I am experiencing some difficulties when trying to calculate vertical  
excitation energies using CASPT2/3. Specifically, whenever I use larger  
basis sets such as aug-cc-pVTZ and aug-cc-pVQZ, some of my excited states  
fail to converge even after 250 or more iterations. I know that the active  
space used is appropriate as I get sensible values with CASSCF, MRCI, AQCC  
and ACPF.

The CASPT calculation gives sensible results for 3 of the 4 excited states  
that I am interested in but fails to converge a  predissociative 1B2 state  
in SO2.

I notice that several people have written to the list before with similar  
convegence issues and was wondering if anybody has found an appropriate  
strategy for getting CASPT2/3 calculations to converge

Regards

-- 
Joseph Lane
Department of Chemistry
University of Otago
P.O. Box 56
Dunedin, New Zealand
ph +64 3 479 5214
email : jlane at alkali.otago.ac.nz