Computational Benchmarking for Ultrafast Electron Dynamics: Wave Function Methods vs Density Functional Theory | JoVE Visualize

Area of Science:

Computational quantum chemistry
Attosecond science
Molecular dynamics

Background:

Understanding attosecond electron dynamics is crucial for studying molecular interactions with intense light.
Accurate computational methods are needed to simulate these ultrafast processes, especially for nonlinear absorption.
Time-dependent density functional theory (TD-DFT) is a widely used but computationally efficient approach for such studies.

Purpose of the Study:

To computationally evaluate the performance of real-time time-dependent density functional theory (TD-DFT) for attosecond electron dynamics.
To analyze the impact of exchange and correlation effects on nonequilibrium electron dynamics.
To assess TD-DFT's accuracy compared to high-level correlated methods like equation-of-motion coupled cluster and complete active space self-consistent field.

Main Methods:

Solving the time-dependent Schrödinger equation for small- and medium-sized molecules (LiH, ABCU) with frozen nuclei.
Comparing TD-DFT results with equation-of-motion coupled cluster singles and doubles (EOM-CCSD) and complete active space multi-configurational self-consistent field (CAS-MCSCF) calculations.
Probing molecules with IR and UV pulses and analyzing the time-dependent dipole moment and its Fourier power spectrum.

Main Results:

TD-DFT qualitatively reproduces attosecond electron dynamics, including nonlinear absorption processes.
TD-DFT shows robust performance across different molecular sizes and pulse polarizations, even for transitions between states of different symmetries.
Excitation energies calculated with TD-DFT remain largely unchanged when excited states are populated, contrary to some previous findings.

Conclusions:

Real-time TD-DFT is a reliable and computationally efficient method for studying attosecond electron dynamics in molecules.
The method's accuracy is validated against more computationally expensive correlated methods.
TD-DFT's performance is consistent regardless of the symmetry of the electronic states involved in transitions.