Reformulation of Time-Dependent Density Functional Theory for Nonperturbative Dynamics: The Rabi Oscillation Problem...

Area of Science:

• Quantum mechanics
• Computational chemistry
• Theoretical physics

Background:

• Time-dependent density functional theory (TDDFT) is a key method for simulating molecular dynamics.
• The adiabatic approximation in TDDFT struggles with nonperturbative dynamics, like Rabi oscillations.
• Accurate simulation of these dynamics is crucial for understanding quantum systems.

Purpose of the Study:

• To reformulate TDDFT for accurate simulation of nonperturbative dynamics.
• To enable TDDFT to predict phenomena like Rabi oscillations.
• To extend the applicability of TDDFT to systems far from equilibrium.

Main Methods:

• Developed a reformulation of TDDFT requiring only response quantities.
• Evaluated the functional on a density near the ground state, not the full nonperturbative density.
• Applied the method to real-time dynamics simulations.

Main Results:

• Successfully predicted Rabi oscillations, previously considered out of reach for TDDFT.
• Demonstrated accurate simulation of a resonantly-driven excitation in Helium.
• Showcased accurate simulation of charge-transfer dynamics in LiCN.

Conclusions:

• The reformulated TDDFT overcomes limitations of the adiabatic approximation for nonperturbative dynamics.
• This advancement significantly expands the predictive power of TDDFT for quantum systems.
• The method provides a reliable approach for simulating complex real-time molecular processes.