TINKTEP: A fully self-consistent, mutually polarizable QM/MM approach based on the AMOEBA force field

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Molecular Mechanics

Background:

• Accurate modeling of molecular interactions is crucial in chemistry and biology.
• Existing QM/MM methods often struggle to fully capture polarization effects between quantum and classical regions.
• The AMOEBA force field offers advanced polarizable modeling for classical systems.

Purpose of the Study:

• To introduce a novel QM/MM approach that allows for mutual polarization between quantum and classical subsystems.
• To integrate the AMOEBA polarizable force field with a linear-scaling DFT method (ONETEP).
• To achieve self-consistent optimization of both quantum and classical degrees of freedom.

Main Methods:

• Coupling a quantum subsystem (ONETEP DFT) with a classical subsystem (AMOEBA force field).
• Utilizing multipolar electrostatics for mutual polarization between QM and MM.
• Employing a total energy minimization scheme with gradient methods for self-consistency.
• On-the-fly distributed multipole analysis to represent the QM subsystem classically.

Main Results:

• Demonstrated simultaneous optimization of quantum and classical degrees of freedom.
• Validated the method for solute-solvent interaction energies of neutral and charged molecules.
• Showcased improved agreement with fully quantum calculations by including explicit MM polarization.

Conclusions:

• The developed QM/MM approach effectively captures mutual polarization, enhancing simulation accuracy.
• This method provides a more rigorous treatment of QM/MM systems, especially for systems with significant charge transfer or polarization.
• The integration of ONETEP and AMOEBA opens new avenues for high-accuracy molecular simulations.