# A DFT-based Tight-Binding Approach to the Self-consistent Description of Molecule Metal-Nanoparticle Interactions

## TL;DR

This paper presents a combined quantum-classical DFTB-based method to model interactions between spherical metal nanoparticles and organic dye molecules, accounting for polarization and electronic effects.

## Contribution

It introduces a self-consistent approach integrating classical multipole polarization with quantum molecular charge density using DFTB, enabling efficient analysis of nanoparticle-molecule interactions.

## Key findings

- Interaction depends on nanoparticle radius and molecule-nanoparticle distance.
- Orientation significantly influences the interaction strength.
- Method successfully applied to different dye molecules.

## Abstract

The interaction within a hybrid system consisting of a spherical metal nanoparticle and a nearby organic dye molecule is formulated in a combined quantum-classical approach. Whereas the nanoparticle's polarization field is treated in classical multipole form, the electronic charge density of the molecule is described quantum mechanically. An efficient solution of the resulting self-consistency problem becomes possible by using the discrete representation of the charge density in terms of atom-centered Mulliken charges within the density functional theory-based tight binding (DFTB) approach. Results for two different dye molecules are presented, which focus on the dependence of the interaction on the nanoparticle's radius, the distance between nanoparticle and molecule and their mutual orientation.