Implementation of Nonadiabatic Molecular Dynamics for Intersystem Crossing Based on a Time-Dependent...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Photophysics

Background:

• Intersystem crossing (ISC) and internal conversion (IC) are crucial nonadiabatic transitions in photochemistry and photobiology.
• Nonadiabatic molecular dynamics (NA-MD) is essential for simulating these dynamic processes.

Purpose of the Study:

• To implement and validate an NA-MD method that treats ISC and IC equally.
• To incorporate spin-orbit coupling calculations within the time-dependent density-functional tight-binding (TD-DFTB) framework.

Main Methods:

• Developed an NA-MD method using TD-DFTB for electronic structure calculations.
• Implemented a spin-orbit coupling algorithm within the TD-DFTB framework.
• Applied the method to simulate ultrafast ISC in 2-nitronaphthalene.

Main Results:

• The TD-DFTB-based NA-MD method successfully treated ISC and IC on an equal footing.
• Calculated spin-orbit coupling trends aligned with those from time-dependent density functional theory (TD-DFT).
• The method accurately reproduced the ultrafast ISC phenomenon observed in 2-nitronaphthalene.

Conclusions:

• The developed NA-MD method provides a computationally efficient and accurate approach for studying nonadiabatic transitions.
• This advancement facilitates deeper understanding of photophysical and photochemical processes involving ISC and IC.