Modeling Ultrafast Electron Dynamics in Strong Magnetic Fields Using Real-Time Time-Dependent Electronic Structure Methods.

Meilani Wibowo,Andrew M Teale,Tom J P Irons

doi:10.1021/acs.jctc.0c01269

Meilani Wibowo, Andrew M Teale + Show 1 more

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https://doi.org/10.1021/acs.jctc.0c01269

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Abstract

An implementation of real-time time-dependent Hartree–Fock (RT-TDHF) and current density functional theory (RT-TDCDFT) for molecules in strong uniform magnetic fields is presented. In contrast to earlier implementations, the present work enables the use of the RT-TDCDFT formalism, which explicitly includes field-dependent terms in the exchange–correlation functional. A range of current-dependent exchange–correlation functionals based on the TPSS functional are considered, including a range-separated variant, which is particularly suitable for application to excited state calculations. The performance of a wide range of propagator algorithms for real-time methods is investigated in this context. A recently proposed molecular orbital pair decomposition analysis allows for assignment of electronic transitions, providing detailed information about which molecular orbitals are involved in each excitation. The application of these methods is demonstrated for the electronic absorption spectra of N2 and H2O both in the absence and in the presence of a magnetic field. The dependence of electronic spectra on the magnetic field strength and its orientation relative to the molecule is studied. The complex evolution of the absorption spectra with magnetic field is rationalized using the molecular orbital pair decomposition analysis, which provides crucial insight in strong fields where the spectra are radically different from their zero-field counterparts.

Highlights

The development of computational methods to study light− matter interactions in the presence of external fields is essential for the understanding of fundamental photophysical processes
Weak-field interactions are well described by perturbation theories such as linear response timedependent Hartree−Fock (LR-TDHF)[1,2] and density functional theory (LR-TDDFT),[3−5] which yield excitation energies and oscillator strengths, and allow excitations to be described in terms of particular transitions between the molecular orbitals involved.[4]
We have presented an implementation of RTTDHF/RT-TD(C)DFT approaches for molecules in strong magnetic fields

Summary

Introduction

The development of computational methods to study light− matter interactions in the presence of external fields is essential for the understanding of fundamental photophysical processes. Weak-field interactions are well described by perturbation theories such as linear response timedependent Hartree−Fock (LR-TDHF)[1,2] and density functional theory (LR-TDDFT),[3−5] which yield excitation energies and oscillator strengths, and allow excitations to be described in terms of particular transitions between the molecular orbitals involved.[4] Recently, linear response (LR) methods have been extended to treat molecular systems in the presence of strong magnetic fields at the Hartree−Fock and density functional levels[6,7] utilizing London atomic orbitals (LAOs) so that the orbitals exhibit a physically correct response to the magnetic field, within a finite basis representation.[8]. RT methods offer advantages for calculating the entire spectra of systems with a high density of states, for which LR methods

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