Simulation of Singlet Exciton Diffusion in Bulk Organic Materials

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Dynamics

Background:

• Exciton transport is key in molecular materials.
• Molecular motion significantly impacts exciton coupling and diffusion.
• Accurate simulations require accounting for nuclear and electronic dynamics.

Purpose of the Study:

• To present a novel nonadiabatic direct dynamics simulation scheme for Frenkel exciton diffusion.
• To incorporate the influence of molecular motion on exciton couplings.
• To enable simultaneous propagation of nuclear and electronic degrees of freedom.

Main Methods:

• Combined quantum-mechanical/molecular mechanics (QM/MM) approach.
• Frenkel Hamiltonian with classical force fields and semiempirical time-dependent density functional tight-binding (TD-DFTB).
• Fewest-switches surface-hopping and Boltzmann-corrected Ehrenfest methods for dynamics propagation.

Main Results:

• Demonstrated a method for simulating exciton diffusion with coupled nuclear-electronic dynamics.
• Applied the scheme to model singlet exciton diffusion in crystalline anthracene.
• Identified strengths and limitations of the developed methodology.

Conclusions:

• The presented scheme effectively simulates Frenkel exciton diffusion by including molecular motion effects.
• This methodology provides a robust tool for studying exciton transport in molecular systems.
• Further refinement can enhance the accuracy and applicability of the simulation approach.