Simulating real-time molecular electron dynamics efficiently using the time-dependent density matrix renormalization group

TL;DR

This paper investigates how to efficiently simulate real-time molecular electron dynamics using the time-dependent density matrix renormalization group (TDDMRG), providing guidelines for parameter choices and demonstrating its application to charge migration in furfural.

Contribution

It establishes convergence guidelines for TDDMRG parameters and introduces a method to optimize orbital selection for accurate electron dynamics simulations.

Findings

TDDMRG parameters significantly influence simulation quality and efficiency.

A new orbital selection method improves the accuracy of electron dynamics simulations.

Application to furfural reveals ultrafast charge migration from sigma to pi states.

Abstract

Compared to ground state electronic structure optimizations, accurate simulations of molecular real-time electron dynamics are usually much more difficult to perform. To simulate electron dynamics, the time-dependent density matrix renormalization group (TDDMRG) has been shown to offer an attractive compromise between accuracy and cost. However, many simulation parameters significantly affect the quality and efficiency of a TDDMRG simulation. So far, it is unclear whether common wisdom from ground state DMRG carries over to the TDDMRG, and a guideline on how to choose these parameters is missing. Here, in order to establish such a guideline, we investigate the convergence behavior of the main TDDMRG simulation parameters, such as time integrator, the choice of orbitals, and the choice of matrix-product-state representation for complex-valued non-singlet states. In addition, we propose a method to select orbitals that are tailored to optimize the dynamics. Lastly, we showcase the TDDMRG by applying it to charge migration ionization dynamics in furfural, where we reveal a rapid conversion from an ionized state with a $\sigma$ character to one with a $\pi$ character within less than a femtosecond.