Fragment Molecular Orbital Nonadiabatic Molecular Dynamics for Condensed Phase Systems

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Molecular Dynamics

Background:

• Simulating nonadiabatic molecular dynamics (NAMD) is crucial for understanding chemical processes in nanoscale and condensed phase systems.
• Accurate electronic structure calculations, including forces and nonadiabatic couplings, are computationally demanding for large systems.
• The fragment molecular orbital (FMO) approximation offers a potential solution for computational efficiency.

Purpose of the Study:

• To develop and validate an efficient method for simulating nonadiabatic molecular dynamics (NAMD).
• To investigate the influence of explicit solvent molecules on excited-state relaxation dynamics.
• To leverage the fragment molecular orbital (FMO) approximation for computational savings.

Main Methods:

• Developed a novel computational approach for efficient NAMD simulations.
• Employed the fragment molecular orbital (FMO) approximation to compute electronic structure, forces, and nonadiabatic couplings.
• Simulated the excited state relaxation of the Fe(CO)4 complex in both gas phase and explicit ethanol solvent environments.

Main Results:

• The developed NAMD method achieved significant computational efficiency.
• Gas-phase relaxation of Fe(CO)4 occurred on a 50 fs timescale, consistent with experimental femtosecond pump-probe spectroscopy.
• Inclusion of ethanol solvent molecules increased the excited state lifetime to 100 fs, aligning with femtosecond X-ray spectroscopy measurements.

Conclusions:

• The FMO-based NAMD method provides an efficient and accurate approach for studying condensed phase dynamics.
• Explicit solvent effects significantly alter excited state relaxation pathways and timescales.
• This technique offers a powerful tool for investigating complex chemical phenomena in realistic environments.