Effects of Domain Morphology on Kinetics of Fluid Phase Separation

TL;DR

This study uses molecular dynamics simulations to explore how the shape of domains influences the speed and mechanism of phase separation in a Lennard-Jones fluid, revealing different growth behaviors depending on density.

Contribution

It demonstrates the impact of domain morphology on phase separation kinetics and identifies a transition from droplet nucleation to elongated structures affecting growth rates.

Findings

Nucleation dominates at low densities with droplet collisions.

Elongated, percolating domains emerge at higher densities.

Growth exponent increases with domain elongation.

Abstract

Kinetics of phase separation in a three dimensional single-component Lennard-Jones fluid, that exhibits vapor-liquid transition, is studied via molecular dynamics simulations after quenching homogeneous systems, of different overall densities, inside the coexistence region. For densities close to the vapor branch of the coexistence curve, phase separation progresses via nucleation of liquid droplets and collisions among them. This is different from the evaporation-condensation mechanism proposed by Lifshitz and Slyozov, even though both lead to power-law growth of average domain size, as a function of time, with an exponent $\alpha=1/3$. Beyond a certain threshold value of the overall density, we observe elongated, percolating domain morphology which suddenly enhances the value of $\alpha$. These results are consistent with some existing theoretical expectations.