Interaction-Driven Phase Separation and Dynamic Scaling in Binary Lennard–Jones Fluids

Abstract

Phase separation in multicomponent fluids is governed by microscopic intermolecular interactions, yet the connection between local structural ordering and macroscopic domain evolution remains incompletely understood. This study employed equilibrium molecular dynamics simulations to investigate the influence of unlike interaction strength and temperature on the structural evolution and coarsening behaviour of a three-dimensional binary Lennard–Jones fluid. Representative simulation snapshots, partial radial distribution functions, concentration fluctuations, cluster statistics, static structure factors and dynamic scaling were combined to quantify phase separation across multiple length scales. Weakening the unlike interaction progressively destabilised the homogeneous mixture, promoting enhanced like-particle coordination, accelerated concentration fluctuations and the formation of interconnected domains. Reciprocal-space analysis showed a systematic shift of the principal structure-factor peak toward lower wave numbers, consistent with continuous domain growth. Despite the faster coarsening observed at weaker unlike interactions, the late-stage evolution followed diffusion-controlled power-law growth with domain-growth exponents close to the classical Lifshitz–Slyozov–Wagner prediction (n 0.30 - 0.34). The collapse of the scaled domain-size and structure-factor data further confirmed dynamic self-similarity during late-stage phase separation. These findings demonstrate that unlike interaction strength primarily controls the onset and timescale of phase separation while preserving the universal scaling behaviour of domain coarsening.