# GW Approximation Coupled with Classical Fluctuating Charges and Dipoles

## TL;DR

This paper introduces a new method combining quantum and classical models to study electron and polarization effects in molecules like phenol and GFP chromophore in water.

## Contribution

A novel multiscale QM/classical methodology using GW and FQ/FQFμ for electron correlation and polarization modeling.

## Key findings

- The model accurately calculates ionization potentials of aqueous phenol.
- The method is applied to study the GFP chromophore in aqueous solution.
- GW and FQ/FQFμ combination captures mutual polarization effects effectively.

## Abstract

We propose a novel multiscale QM/classical methodology
based on
the GW approximation combined with the fluctuating charges (FQ) and
fluctuating charges and dipoles (FQFμ) force fields. The GW
approximation is exploited to capture electron correlation effects,
while FQ or FQFμ is used to model the mutual polarization effects
between the quantum GW system and its surrounding environment in a
multiscale fashion. The model is validated through test calculations
of ionization potentials of aqueous phenol and applied to the Green
Fluorescent Protein (GFP) chromophore (4-hydroxybenzylidene-1,2-dimethylimidazolinonep-HDBI)
in aqueous solution.