Simulating Electron Dynamics with GPU-Accelerated Real-Time Tamm-Dancoff Approximation

TL;DR

This paper introduces a GPU-accelerated real-time Tamm-Dancoff approximation method for simulating electron dynamics, improving the efficiency and capability of modeling large molecules and intense field interactions.

Contribution

The paper develops and demonstrates a GPU-accelerated real-time Tamm-Dancoff approximation for electron dynamics, overcoming limitations of previous methods in intense fields.

Findings

Successful simulation of large organic molecule spectra

Observation of Rabi oscillations and AC Stark effect

Enhanced simulation speed and scale with GPU acceleration

Abstract

Time-dependent electronic structure methods provide an efficient, accurate, and robust alternative to traditional time dependent methods for computing both linear and non-linear optical properties. With this in mind, we have developed the real-time Tamm-Dancoff approximation (RT-TDA). This is an approach to model electron dynamics by propagating the linear-response time-dependent density functional theory (LR-TDDFT) amplitudes within the Tamm-Dancoff approximation (TDA) and adiabatic approximation. Because the electronic structure is propagated in real-time in a many-electron basis, RT-TDA overcomes known limitations of adiabatic Kohn-Sham RT-TDDFT for describing dynamics in intense fields. Acceleration by graphic processing units (GPUs) enables simulations of larger molecules and on longer timescales. To demonstrate the utility of our approach, we present the calculations of the linear absorption spectrum of a large organic molecule (120 heavy atoms), of Rabi oscillations, and of nonlinear 2-photon absorption, in which we observe the AC Stark effect.