Role of enviromental dynamic polarizability in static excited state properties of embedded molecular systems: Application to disordered fluorographene systems

TL;DR

This paper extends the polarizable QM/MM approach by incorporating frequency-dependent atomic polarizabilities, improving the modeling of environmental effects on excited states in embedded systems, demonstrated on fluorographene-based systems.

Contribution

The authors develop a quantum polarizable atom model that generalizes classical polarizable QM/MM, including frequency dependence, and apply it to fluorographene systems to better understand environmental effects.

Findings

Frequency dependence of atomic polarizabilities is crucial for accurate excited state modeling.

The new model aligns well with full quantum chemistry calculations.

Classical polarizable atom models are a limiting case of the proposed approach.

Abstract

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 loss of computational simplicity of the QM/MM approach. The classical polarizable atom description used in polarizable QM/MM approach can be obtained as a limiting case of the present model. This enables us to pinpoint approximations and assumptions about the system inherent to classical polarizable atom description of the environment. We apply our method to fluorographene (FG) based systems to investigate effects of the FG sheet on excited state properties of impurities on the FG surface. Comparison to full quantum chemistry calculations and to the standard polarizable QM/MM approach on disordered fluorograhene clusters reveals the importance of frequency dependence of atomic polarizabilities for the proper treatment of the effects of the environment on both the transition energy shifts and the interaction energies.