Hamiltonian Grid-Based QM/MM Method with Mean-Field Embedding for Simulating Arbitrary Slab Geometries

Area of Science:

• Computational Chemistry
• Materials Science
• Surface Science

Background:

• Quantum mechanics/molecular mechanics (QM/MM) is vital for modeling solid-surface interfaces.
• Mean-field QM/MM offers efficient free energy calculations but faces sampling challenges.
• Accurate simulation of interfacial atomic configurations is crucial for understanding material properties.

Purpose of the Study:

• To develop a grid-based mean-field QM/MM method for enhanced solid-surface simulations.
• To enable flexible modeling of complex interfaces in arbitrary simulation cells.
• To improve the efficiency and rigor of free energy calculations at interfaces.

Main Methods:

• A novel grid-based mean-field QM/MM approach utilizing particle-mesh in fractional coordinates.
• Employing a C^n class assignment function (n>=1) for MM atom charge distribution on grid points.
• Analytical derivation of QM-MM electrostatic forces from total energy using assignment function derivatives.

Main Results:

• The proposed method ensures energy conservation and correct interfacial distribution.
• Reliable dynamics of medium atoms are achieved through long-time simulations.
• Demonstrated feasibility of numerically rigorous free energy calculations using analytical gradients.

Conclusions:

• The grid-based mean-field QM/MM method provides a robust framework for simulating solid-medium interfaces.
• This advancement facilitates accurate and efficient free energy calculations for complex systems.
• The Hamiltonian formalism ensures the reliability and accuracy of the simulation dynamics.