Nonadiabatic molecular dynamics simulations based on time-dependent density functional tight-binding method.

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Materials Science

Background:

• Nonadiabatic excited state molecular dynamics are crucial for understanding photophysical and photochemical processes like exciton dynamics and charge transport.
• Accurate simulation of these dynamics is essential for designing new materials with specific light-interacting properties.

Purpose of the Study:

• To develop an efficient and accurate nonadiabatic molecular dynamics (NAMD) simulation method.
• To improve computational efficiency in simulating excited-state dynamics.

Main Methods:

• Utilized time-dependent density functional tight-binding (TDDFTB) theory for adiabatic electronic structure calculations.
• Employed the trajectory surface hopping algorithm to treat nonadiabatic effects.
• Derived analytical expressions for nonadiabatic couplings and used molecular orbital overlaps for faster calculations.

Main Results:

• Developed an efficient NAMD method based on TDDFTB.
• Implemented analytical nonadiabatic couplings and optimized calculations using molecular orbital overlaps.
• Demonstrated the method's accuracy by simulating the photoinduced dynamics of benzene, showing good agreement with more computationally expensive methods.

Conclusions:

• The proposed TDDFTB-based NAMD method is computationally efficient and accurate for simulating excited-state dynamics.
• This methodology serves as a valuable tool for predicting photophysical and photochemical properties of complex materials.
• The implementation in NEXMD software enhances accuracy and handles complex crossing scenarios.