An Accurate, Affordable Density Functional Tight-Binding Model for Excited State Hydrocarbon Polymer Molecular...

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Physical Chemistry

Background:

• Accurate simulation of hydrocarbon excited state dynamics is crucial for understanding photochemistry.
• Existing methods like time-dependent density functional theory (TD-DFT) are computationally expensive for long timescales.

Purpose of the Study:

• To develop a highly efficient and accurate computational model for hydrocarbon excited state dynamics.
• To enable simulations of photochemical processes and radiation scattering over longer timescales.

Main Methods:

• Developed a density functional tight-binding (DFTB) model.
• Referenced high-level electronic structure theory for model parameters.
• Incorporated a many-body repulsive energy term.
• Validated the model using n-octane geometry optimizations, bond dissociation scans, and vibrational frequencies.

Main Results:

• The developed DFTB model achieves accuracy comparable to hybrid TD-DFT methods.
• The model demonstrates a computational efficiency approximately 1000 times greater than hybrid TD-DFT.
• Successful validation against n-octane properties confirms model reliability.

Conclusions:

• The new DFTB model offers a significant advancement in simulating hydrocarbon excited state dynamics.
• This approach facilitates longer timescale simulations, opening new avenues in photochemistry research.
• The model provides a computationally feasible tool for studying excited state processes in hydrocarbons.