Simulation of 24,000 Electrons Dynamics: Real-Time Time-Dependent Density Functional Theory (TDDFT) with the Real-Space Multigrids (RMG)

TL;DR

This paper introduces a real-time TDDFT module within the RMG code, enabling efficient, stable simulations of electronic dynamics in diverse molecular and nanoscale systems, with demonstrated scalability and accuracy.

Contribution

The paper presents a novel RT-TDDFT implementation in RMG that offers improved stability, scalability, and applicability to large and complex systems compared to existing methods.

Findings

Excellent agreement with established TDDFT methods

Stable long-term simulations with minimal energy drift

Scalable to systems with thousands of atoms

Abstract

We present the theory, implementation, and benchmarking of a real-time time-dependent density functional theory (RT-TDDFT) module within the RMG code, designed to simulate the electronic response of molecular systems to external perturbations. Our method offers insights into non-equilibrium dynamics and excited states across a diverse range of systems, from small organic molecules to large metallic nanoparticles. Benchmarking results demonstrate excellent agreement with established TDDFT implementations and showcase the superior stability of our time-integration algorithm, enabling long-term simulations with minimal energy drift. The scalability and efficiency of RMG on massively parallel architectures allow for simulations of complex systems, such as plasmonic nanoparticles with thousands of atoms. Future extensions, including nuclear and spin dynamics, will broaden the applicability of this RT-TDDFT implementation, providing a powerful toolset for studies of photoactive materials, nanoscale devices, and other systems where real-time electronic dynamics is essential.