# Aging Phenomena during Phase Separation in Fluids: Decay of autocorrelation for vapor-liquid transitions

## TL;DR

This study uses molecular dynamics simulations to analyze aging phenomena during vapor-liquid phase separation in fluids, revealing universal power-law decay of autocorrelation functions despite different morphologies and growth mechanisms.

## Contribution

It demonstrates that the decay of the order-parameter autocorrelation follows a power-law in both disconnected and percolating morphologies, highlighting universality in coarsening dynamics.

## Key findings

- Power-law decay observed in disconnected morphology
- Complex decay behavior in percolating structure
- Finite-size scaling reveals strong preasymptotic corrections

## Abstract

We performed molecular dynamics simulations to study relaxation phenomena during vapor-liquid transitions in a single component Lennard-Jones system. Results from two different overall densities are presented; one in the neighborhood of the vapor branch of the coexistence curve and the other being close to the critical density. The nonequilibrium morphologies, growth mechanisms and growth laws in the two cases are vastly different. In the low density case growth occurs via diffusive coalescence of droplets in a disconnected morphology. On the other hand, the elongated structure in the higher density case grows via advective transport of particles inside the tube-like liquid domains. The objective in this work has been to identify how the decay of the order-parameter autocorrelation, an important quantity to understand aging dynamics, differs in the two cases. In the case of the disconnected morphology, we observe a very robust power-law decay, as a function of the ratio of the characteristic lengths at the observation time and at the age of the system, whereas the results for the percolating structure appear rather complex. To quantify the decay in the latter case, unlike standard method followed in a previous study, here we have performed a finite-size scaling analysis. Outcome of this analysis shows the presence of a strong preasymptotic correction, while revealing that in this case also, albeit in the asymptotic limit, the decay follows a power-law. Even though the corresponding exponents in the two cases differ drastically, this study, combined with a few recent ones, suggests that power-law behavior of this correlation function is rather universal in coarsening dynamics.