Spin-Orbit Couplings for Nonadiabatic Molecular Dynamics at the ΔSCF Level

Area of Science:

• Theoretical Chemistry
• Computational Quantum Chemistry
• Electronic Structure Theory

Background:

• Calculating spin-orbit coupling (SOC) is crucial for understanding intersystem crossing (ISC) in excited electronic states.
• Existing methods like time-dependent density functional theory (TD-DFT) can be computationally expensive.
• Delta self-consistent field (ΔSCF) offers a computationally efficient alternative for excited states.

Purpose of the Study:

• To present a novel procedure for calculating spin-orbit coupling (SOC) at the delta self-consistent field (ΔSCF) level of theory.
• To enable efficient, full-atomistic nonadiabatic molecular dynamics (NAMD) simulations incorporating ISC.
• To provide a framework for calculating observables within the ΔSCF method.

Main Methods:

• The ΔSCF method is employed to obtain singlet and triplet excited electronic states.
• Excited states are expanded as linear combinations of Slater determinants using ground state Kohn-Sham orbitals.
• This approach addresses the nonorthogonality between ground and excited states, enabling observable calculations.

Main Results:

• The developed ΔSCF procedure successfully calculates SOC terms.
• Comparison with TD-DFT for formaldehyde shows good agreement for calculated observables.
• The method provides energies, gradients, nonadiabatic couplings, and SOC terms at the ΔSCF level.

Conclusions:

• The presented ΔSCF procedure is effective for calculating SOC and other key components for NAMD.
• This method facilitates efficient simulations of intersystem crossing (ISC) in complex systems, particularly in condensed phases.
• The framework extends ΔSCF capabilities for calculating molecular dynamics observables.