Microphase separation in mixtures of Lennard-Jones particles

Abstract

Several binary systems composed of one-centre Lennard-Jones particles with identical size and interaction parameters, σ₁₁, σ₂₂, ε₁₁, ε₂₂ and ε₁₂, but different cross diameter parameters σ₁₂, were simulated using an extended version of the Gibbs ensemble Monte Carlo method, in an attempt to predict the fluid phase behaviour in such systems. No liquid–liquid phase separation was found in the mixtures but all cases studied exhibit a structured liquid phase in equilibrium with its vapour. The domain shapes and patterns observed both in three- and two-dimensional simulations (stripe and bubble phases) were interpreted within the framework of the phenomenology of modulated phases, also known as microphase separated fluids. The appearance of stripe patterns occurs when σ₁₂ is larger than σ₁₁, while the bubble phases are characteristic of systems with σ₁₂ smaller than σ₁₁.