Nonadiabatic Dynamics for Electrons at Second-Order: Real-Time TDDFT and OSCF2

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Theoretical Physics

Background:

• Simulating nonradiative relaxation and dephasing is crucial for understanding electronic dynamics in molecular systems.
• Existing methods often lack systematic derivation or proper relaxation to thermal distributions.
• Accurate modeling requires integrating electronic structure theory with environmental effects.

Purpose of the Study:

• To develop and implement a novel computational model for simulating nonradiative relaxation and dephasing.
• To combine real-time Hartree-Fock and Density Functional Theory (DFT) with open-systems theory.
• To provide a computationally efficient and systematically derived approach for realistic molecular systems.

Main Methods:

• Integration of real-time Hartree-Fock and DFT with a new open-systems theory for electronic dynamics.
• Development of an atomistic, all-electron quantum chemistry code with an atom-centered, nonempirical thermal environment model.
• Implementation of a production-quality, O(N^3) closed-shell model, time-dependent open self-consistent field at second order (OSCF2).

Main Results:

• The OSCF2 model systematically relaxes noninteracting electrons to a Fermi-Dirac distribution.
• The OSCF2 approach is computationally inexpensive compared to standard real-time TDHF/TDDFT.
• Demonstrated OSCF2 convergence to the stationary self-consistent field (SCF) ground state under specific conditions.
• Calculated linear-response spectra incorporating bath dynamics and showed OSCF2's utility in correcting ground-state DFT calculations.

Conclusions:

• The developed OSCF2 model offers an efficient and accurate method for simulating electronic dynamics, including nonradiative relaxation and dephasing.
• The approach provides a robust framework for studying finite-temperature effects in molecular systems.
• This work enables more accurate predictions of molecular properties and corrections to standard DFT calculations.