Polarizable Embedding for Excited-State Reactions: Dynamically Weighted Polarizable QM/MM.

Recent interest in polarizable embedding methods for electronic excited states has so far been focused on optical absorption and emission spectra calculations. To explore the suitability of these methods for excited-state reactions, we constructed a simple molecular system with an electronic crossing coupled to a polarizable species: the triatomic LiFBe. We found that current polarizable QM/MM methods inadequately describe the potential energy surfaces in this system, particularly close to the electronic crossing, so we developed a new polarizable embedding method called dynamically weighted polarizable QM/MM. The new method reproduces the potential energy surfaces of LiFBe from full-system multireference configuration interaction singles and doubles calculations with near-quantitative accuracy.