Analytic non-adiabatic derivative coupling terms for spin-orbit MRCI wavefunctions. II. Derivative coupling terms and...

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Spectroscopy

Background:

• Calculating nonadiabatic derivative coupling terms (DCTs) is crucial for understanding molecular dynamics.
• Spin-orbit interactions significantly influence electronic structure and reaction pathways.
• Accurate DCTs are essential for high-fidelity simulations of chemical processes.

Purpose of the Study:

• To review and present a method for calculating analytic nonadiabatic derivative coupling terms (DCTs).
• To apply this method to spin-orbit multi-reference configuration interaction wavefunctions.
• To compare the results with existing theoretical approaches.

Main Methods:

• Analytic calculation of DCTs for spin-orbit multi-reference configuration interaction.
• Application of the Stuttgart basis set for KHe calculations.
• Comparison with Nikitin's 3x3 model and Werner's analysis of configuration interaction coefficients.

Main Results:

• The analytic DCTs for KHe were calculated using the reviewed method.
• Excellent agreement was found between the integrated radial analytic DCTs from different methods.
• Nonadiabatic energy surfaces for KHe were successfully generated.

Conclusions:

• The reviewed method provides accurate analytic DCTs for spin-orbit systems.
• The results validate the theoretical framework for describing nonadiabatic couplings.
• This work facilitates more precise theoretical studies of molecular systems with spin-orbit coupling.