Natural Orbital Branching Scheme for Time-Dependent Density Functional Theory Nonadiabatic Simulations

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Theoretical Physics

Background:

• Real-time time-dependent density functional theory (rt-TDDFT) is widely applied but lacks features for detailed nonadiabatic molecular dynamics.
• Conventional methods struggle with state transitions, decoherence, and stochastic nuclear trajectories, especially in large systems.

Purpose of the Study:

• To develop new algorithms for nonadiabatic rt-TDDFT simulations that incorporate key missing features.
• To address limitations in describing detailed balance, decoherence, and wave function evolution in complex molecular systems.

Main Methods:

• Introduced a Boltzmann factor algorithm for decoherence and detailed balance with mean-field nuclear dynamics.
• Developed the natural orbital branching (NOB) formalism using a time-dependent density matrix and natural orbitals for wave function collapse, decoherence, detailed balance, and trajectory branching.

Main Results:

• The Boltzmann factor algorithm adds decoherence and detailed balance to carrier dynamics.
• The NOB formalism successfully implements decoherence, detailed balance, and trajectory branching.
• Both methods were tested on molecule radiolysis decay, showing applicability to complex fragmentation pathways.

Conclusions:

• The new algorithms significantly advance nonadiabatic rt-TDDFT simulations.
• NOB provides a comprehensive approach for studying complex molecular dynamics, including radiolysis.
• NOB maintains computational efficiency comparable to standard rt-TDDFT.