Subsystem real-time Time Dependent Density Functional Theory

TL;DR

This paper extends Frozen Density Embedding to real-time TDDFT, enabling simulation of dynamic interactions and energy transfer between subsystems with improved physical insight and computational efficiency.

Contribution

The novel extension allows real-time evolution of embedded Kohn-Sham systems with dynamic embedding potentials, enhancing the analysis of excitation energy transfer and optical spectra.

Findings

Demonstrated energy transfer in Na4 cluster

Showed impact of dynamic embedding on optical spectra

Validated the importance of full dynamic response

Abstract

We present the extension of Frozen Density Embedding (FDE) theory to real-time Time Dependent Density Functional Theory (rt-TDDFT). FDE a is DFT-in-DFT embedding method that allows to partition a larger Kohn-Sham system into a set of smaller, coupled Kohn-Sham systems. Additional to the computational advantage, FDE provides physical insight into the properties of embedded systems and the coupling interactions between them. The extension to rt-TDDFT is done straightforwardly by evolving the Kohn-Sham subsystems in time simultaneously, while updating the embedding potential between the systems at every time step. Two main applications are presented: the explicit excitation energy transfer in real time between subsystems is demonstrated for the case of the Na$_4$ cluster and the effect of the embedding on optical spectra of coupled chromophores. In particular, the importance of including the full dynamic response in the embedding potential is demonstrated.