Effects of structural inhomogeneity on equilibration processes in Langevin dynamics

Area of Science:

• Computational physics
• Statistical mechanics
• Fluid dynamics

Background:

• Computer simulations provide fundamental insights into atomic and molecular mechanisms in fluids.
• Understanding relaxation processes toward steady physical states is crucial in fluid dynamics.

Purpose of the Study:

• To investigate the effect of initial state configurations on equilibrium decay rates in Langevin canonical ensemble simulations.
• To derive a relationship between system relaxation time and radial distribution function.

Main Methods:

• Molecular-dynamics simulations were employed.
• An original expression relating system relaxation time (τ_{sys}) and radial distribution function (g(r)) was derived.
• Simulations were conducted in near-zero and high-density limits.

Main Results:

• Slightly inhomogeneous initial states lead to significantly longer system relaxation times (τ_{sys}) compared to homogeneous states.
• System relaxation time (τ_{sys}) increases with the Langevin coupling constant (γ) for inhomogeneous initial states.
• During structural equilibration, the radial distribution function (g(r)) at large distances approaches 1 from above for inhomogeneous cases and from below for homogeneous cases.

Conclusions:

• Initial density fluctuations play a critical role in the dynamics of fluid equilibration.
• The derived relationship provides a new tool for analyzing relaxation dynamics in complex fluid systems.
• These findings have implications for understanding non-equilibrium processes in molecular simulations.