LVC/MM: A Hybrid Linear Vibronic Coupling/Molecular Mechanics Model with Distributed Multipole-Based Electrostatic...

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Molecular Dynamics

Background:

• Accurate modeling of electronic states in condensed phases is crucial for understanding chemical processes.
• Existing methods often struggle to balance accuracy and computational efficiency for complex environments.

Purpose of the Study:

• To introduce a novel hybrid linear vibronic coupling/molecular mechanics (LVC/MM) method.
• To integrate this method into the Surface Hopping Including Arbitrary Coupling (SHARC) molecular dynamics package.
• To enhance the simulation of chemical dynamics in condensed-phase environments.

Main Methods:

• Developed a theoretical framework for LVC/MM with electrostatic embedding.
• Utilized distributed multipole expansions (DMEs) up to quadrupoles for electronic state representation.
• Extended Restrained Electrostatic Potential (RESP) fitting for higher-order multipoles.
• Implemented roto-translational invariance, QM/MM, OpenMM interface, and liquid droplet simulations in SHARC.

Main Results:

• The LVC/MM method accurately reproduces solvation structure and energetics for rigid solutes.
• Errors were on the order of 1-2 kcal/mol compared to a BP86/MM reference.
• The SHARC implementation demonstrates high efficiency, enabling nanosecond-scale simulations within days.

Conclusions:

• The LVC/MM method provides a computationally efficient and accurate approach for molecular dynamics simulations.
• This framework significantly advances the capability to model complex chemical systems in solution.
• The implemented features in SHARC open new possibilities for studying condensed-phase dynamics.