Using all-singles CI and random phase approximations in studies of light absorption of large conjugated systems for PPP and INDO/S methods

COMP 286

John M. McKelvey, McKelvey Computational Chemistry, 861 Bennett Rd., Carmel, IN 46032, Sergei Tretiak, Theoretical Division, Los Alamos National Laboratory, Mail stop B268, Los Alamos, NM 87545, and Stefan Grimme, Organisch-Chemisches Institut, University of Muenster, Corrensstrasse 40, Muenster, 48149, Germany.
Descriptions of light absorption of closed shell ground state molecules using SCF-CI methods are most often done using the well known pi-electron Pariser-Parr-Pople method, and Zerner's INDO/S all-valence electron method. Errors in the PPP and INDO/S methods as typically used can be 100NM to 350NM. This work will describe recent studies using all-singles SCF-CI and SCF-RPA approaches that can reduce such errors by at least an order of magnitude, if not two, and also are an order of magnitude faster. Solvation effects on the ground and excited state electronic energies have been investigated using COSMO.