Many-electron dynamics in laser-driven molecules: wavefunction theory vs. density functional theory.

Area of Science:

• Quantum Chemistry
• Theoretical Physics
• Computational Chemistry

Background:

• Accurate theoretical modeling of laser-driven electron dynamics in molecules is crucial.
• Time-Dependent Configuration Interaction Singles (TD-CIS) and Real-Time Time-Dependent Density Functional Theory (RT-TD-DFT) are leading computational methods.

Purpose of the Study:

• To compare the performance of TD-CIS/AO and RT-TD-DFT/Grid for simulating molecular electron dynamics.
• To evaluate their accuracy in predicting bound electron motion and High Harmonic Generation (HHG).

Main Methods:

• Comparison of TD-CIS/AO and RT-TD-DFT/Grid using H2 and C2H2Cl2 molecules.
• Simulation of state-to-state transitions with resonant (π-pulses) and non-resonant laser fields.
• Analysis of time-dependent energies, dipole moments, and HHG spectra.

Main Results:

• TD-CIS accurately captures population inversion for bound state transitions, unlike RT-TD-DFT.
• Both methods show good agreement for lower harmonics in HHG spectra under non-resonant conditions.
• Deviations increase for higher harmonics and low laser intensities; TD-CIS/AO is computationally more efficient.

Conclusions:

• TD-CIS/AO provides reliable results for bound electron dynamics and HHG, showing good agreement with RT-TD-DFT/Grid.
• TD-CIS/AO demonstrates superior computational efficiency compared to RT-TD-DFT/Grid for the tested systems.
• The study highlights the strengths and limitations of both WFT and DFT methods in molecular electron dynamics.