Optimal Temperature Evaluation in Molecular Dynamics Simulations with a Large Time Step.

Area of Science:

• Computational Chemistry
• Molecular Dynamics Simulations
• Statistical Mechanics

Background:

• Accurate temperature evaluation is vital for isothermal-isobaric molecular dynamics (MD) simulations.
• Conventional kinetic energy-based temperature estimation often fails to satisfy Tolman's equipartition theorem, especially with larger time steps.
• This limitation impacts the reliability of simulation results for various molecular systems.

Purpose of the Study:

• To develop a novel, computationally inexpensive method for accurate temperature evaluation in MD simulations.
• To ensure the accurate estimation of temperature, satisfying Tolman's equipartition theorem.
• To provide a robust temperature estimator applicable to diverse molecular systems.

Main Methods:

• Introduced two types of kinetic energy calculations: full-time step (underestimates temperature) and half-time step (overestimates temperature).
• Combined these kinetic energies to derive an optimal instantaneous temperature estimator.
• Validated the method using a 1D harmonic oscillator, pure water, BPTI protein in water, and a DPPC lipid bilayer system.

Main Results:

• The optimal temperature estimator achieves accuracy up to the third order of the time step.
• The proposed method better satisfies the equipartition theorem compared to existing techniques.
• Accurate physical properties were reproduced for time steps up to 5 fs across all tested systems.

Conclusions:

• The novel optimal temperature estimator offers superior accuracy and reliability in MD simulations.
• This method enhances the control of isothermal-isobaric conditions without increasing computational cost.
• The findings are significant for improving the fidelity of molecular simulations in various scientific domains.