Velocity-gauge real-time time-dependent density functional tight-binding for large-scale condensed matter systems

TL;DR

This paper introduces a velocity-gauge real-time TDDFT method within the DFTB+ software, enabling efficient electron dynamics simulations of large-scale condensed matter systems with thousands of atoms, including complex materials and defects.

Contribution

The authors develop and implement a novel VG-rtTDDFTB approach in open-source DFTB+ for large-scale electron dynamics simulations, demonstrating its accuracy and scalability.

Findings

Successfully simulated laser-induced electron dynamics in a 512-atom amorphous silicon supercell.

The method scales favorably with system size, enabling simulations of thousands of atoms.

Benchmark results show good agreement with more accurate methods.

Abstract

We present a new velocity-gauge real-time, time-dependent density functional tight-binding (VG-rtTDDFTB) implementation in the open-source DFTB+ software package (https://dftbplus.org) for probing electronic excitations in large, condensed matter systems. Our VG-rtTDDFTB approach enables real-time electron dynamics simulations of large, periodic, condensed matter systems containing thousands of atoms with a favorable computational scaling as a function of system size. We provide computational details and benchmark calculations to demonstrate its accuracy and computational parallelizability on a variety of large material systems. As a representative example, we calculate laser-induced electron dynamics in a 512-atom amorphous silicon supercell to highlight the large periodic systems that can be examined with our implementation. Taken together, our VG-rtTDDFTB approach enables new electron dynamics simulations of complex systems that require large periodic supercells, such as crystal defects, complex surfaces, nanowires, and amorphous materials.