Metastable liquid lamellar structures in binary and ternary mixtures of Lennard-Jones fluids

TL;DR

This study uses molecular dynamics simulations to reveal that binary and ternary Lennard-Jones fluid mixtures form metastable lamellar structures in coexistence with vapor within a specific temperature range, with stability increasing at lower temperatures.

Contribution

It demonstrates the formation and stability of metastable liquid lamellar structures in Lennard-Jones mixtures, a novel insight into phase coexistence and structure in such systems.

Findings

Metastable lamellar states form in mixtures between 78°C and 102°C.

Lamellar states remain stable for up to 80 ns at temperatures below 90°C.

States become more well-defined and stable as temperature decreases.

Abstract

We have carried out extensive equilibrium molecular dynamics (MD) simulations to investigate the Liquid-Vapor coexistence in partially miscible binary and ternary mixtures of Lennard-Jones (LJ) fluids. We have studied in detail the time evolution of the density profiles and the interfacial properties in a temperature region of the phase diagram where the condensed phase is demixed. The composition of the mixtures are fixed, 50% for the binary mixture and 33.33% for the ternary mixture. The results of the simulations clearly indicate that in the range of temperatures $78 < T < 102 ^{\rm o}$K, --in the scale of argon-- the system evolves towards a metastable alternated liquid-liquid lamellar state in coexistence with its vapor phase. These states can be achieved if the initial configuration is fully disordered, that is, when the particles of the fluids are randomly placed on the sites of an FCC crystal or the system is completely mixed. As temperature decreases these states become very well defined and more stables in time. We find that below $90 ^{\rm o}$K, the alternated liquid-liquid lamellar state remains alive for 80 ns, in the scale of argon, the longest simulation we have carried out. Nonetheless, we believe that in this temperature region these states will be alive for even much longer times.