Resolving the Notorious Case of Conical Intersections
for Coupled Cluster Dynamics
KjønstadEirik
F.
KochHenrik
2017
The
motion of electrons and nuclei in photochemical events often
involves conical intersections, or degeneracies between electronic
states. They serve as funnels in nuclear relaxation processes where
the electrons and nuclei couple nonadiabatically. Accurate ab initio
quantum chemical models are essential for interpreting experimental
measurements of such phenomena. In this Letter, we resolve a long-standing
problem in coupled cluster theory, presenting the first formulation
of the theory that correctly describes conical intersections between
excited electronic states of the same symmetry. This new development
demonstrates that the highly accurate coupled cluster theory can be
applied to describe dynamics on excited electronic states involving
conical intersections.