Aufbau Suppressed Coupled Cluster As a Post-Linear-Response Method

We investigate the ability of Aufbau suppressed coupled
cluster
theory to act as a post-linear-response correction to widely used
linear response methods for electronically excited states. We find
that the theory is highly resilient to shortcomings in the underlying
linear response method, with final results from less accurate starting
points nearly as good as those from the best starting points. This
pattern is especially stark in charge transfer states, where the approach
converts starting points with multi-eV errors into post-linear-response
results with errors on the order of 0.1 eV. These findings highlight
the ability of Aufbau suppressed coupled cluster to perform its own
orbital relaxations and raise the question of whether initializing
it with an orbital relaxed reference is worth the trouble.