2023

We present an extension of the standard polarizable quantum mechanic/molecular mechanics (QM/MM) approach for treating environmental effects on excited state properties of embedded systems. A quantum polarizable atom model is derived from a full quantum description of the environment using perturbation theory for the system-environment coupling.

Our model provides a more general description of the environment, including frequency-dependent atomic polarizabilities, without the loss of computational simplicity of the QM/MM approach. The classical polarizable atom description, used in the polarizable QM/ MM approach, can be obtained as a limiting case of the present model.

This result enables us to pinpoint approximations and assumptions about the system inherent to a classical polarizable atom description of the environment. We apply our method to fluorographene (FG)-based systems to investigate the effects of the FG sheet on excited state properties of impurities on the FG surface.

The comparison to full quantum chemistry calculations and to the standard polarizable QM/MM approach on disordered fluorographene clusters reveals the importance of the frequency dependence of atomic polarizabilities for a proper treatment of the effects of the environment on both the transition energy shifts and the interaction energies.