Elastic Collision Based Dynamic Partitioning Scheme for Hybrid Simulations.

Area of Science:

• Computational Chemistry and Physics
• Molecular Dynamics Simulations

Background:

• Hybrid simulations (e.g., QM/MM) partition systems for varied theoretical treatments.
• Evaluating boundary interactions and particle crossing in hybrid simulations presents challenges.
• Existing methods like FIRES use harmonic restraints, potentially causing particle density anomalies.

Purpose of the Study:

• To develop a novel constraint approach for hybrid simulations that prevents particle crossing.
• To introduce the scattering-adapted flexible inner region ensemble separator (SAFIRES) method.
• To ensure accurate thermodynamic properties and conserve energy in partitioned simulations.

Main Methods:

• SAFIRES implements a constraint where particles instantaneously scatter from the boundary.
• Utilizes a variable-time-step propagation algorithm that scales automatically for collision detection.
• Reduces to Langevin dynamics or velocity Verlet algorithms under specific parameter settings.

Main Results:

• SAFIRES accurately reproduces average ensemble statistics in homogeneous Lennard-Jones liquid and TIP4P water simulations.
• Simulations of a Lennard-Jones liquid at a solid-liquid interface show no significant deviations in particle density.
• Energy conservation is maintained when coupling to the heat bath is deactivated.

Conclusions:

• The SAFIRES method provides an accurate and efficient approach for hybrid simulations.
• It overcomes limitations of previous methods by preventing particle crossing and maintaining simulation integrity.
• SAFIRES is applicable to various systems, including solid-liquid interfaces, enhancing the reliability of computational studies.