Accurate Computation of Nonadiabatic Coupling with Projector Augmented-Wave Pseudopotentials.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Nonadiabatic molecular dynamics (NAMD) combined with real-time time-dependent density functional theory (RT-TDDFT) advances excited-state dynamics modeling.
• Accurate and efficient evaluation of nonadiabatic coupling (NAC) is a key challenge in RT-TDDFT, especially with projector augmented-wave (PAW) pseudopotentials and planewave basis sets.

Purpose of the Study:

• To develop a rigorous method for calculating NAC with PAW wave functions.
• To demonstrate an efficient approximation for NAC evaluation that maintains high accuracy.
• To validate the approach by comparing pseudo- and all-electron calculations across diverse systems.

Main Methods:

• Developed a rigorous method for NAC evaluation within the PAW formalism.
• Implemented an efficient approximation to the rigorous NAC calculation.
• Performed extensive validation by calculating NAC matrix elements for six representative systems using both pseudo- and all-electron wave functions.

Main Results:

• The developed method allows for rigorous NAC computation with PAW wave functions.
• An efficient NAC approximation yields results comparable to the rigorous all-electron calculation.
• Deviations in the approximate NAC were most significant when d-electrons participated in electronic transitions.

Conclusions:

• The presented approach offers a rigorous and practical methodology for numerical NAC computation in Kohn-Sham theory.
• The efficient approximation provides a valuable tool for simulating excited-state dynamics in complex systems.
• This work facilitates more accurate and accessible modeling of nanoscale and condensed matter dynamics.