Excited State-Specific CASSCF Theory for the Torsion of Ethylene.
Published version
Peer-reviewed
Repository URI
Repository DOI
Type
Change log
Authors
Abstract
State-specific complete active space self-consistent field (SS-CASSCF) theory has emerged as a promising route to accurately predict electronically excited energy surfaces away from molecular equilibria. However, its accuracy and practicality for chemical systems of photochemical interest have yet to be fully determined. We investigate the performance of the SS-CASSCF theory for the low-lying ground and excited states in the double bond rotation of ethylene. We show that state-specific approximations with a minimal (2e,2o) active space provide comparable accuracy to state-averaged calculations with much larger active spaces, while optimizing the orbitals for each excited state significantly improves the spatial diffusivity of the wave function. However, the incorrect ordering of state-specific solutions causes excited state solutions to coalesce and disappear, creating unphysical discontinuities in the potential energy surface. Our findings highlight the theoretical challenges that must be overcome to realize practical applications of state-specific electronic structure theory for computational photochemistry.
Description
Publication status: Published
Keywords
Journal Title
Conference Name
Journal ISSN
1549-9626
Volume Title
Publisher
Publisher DOI
Sponsorship
University of Cambridge (NA)