Free energy landscapes, nucleation, and morphological stability of biphasic nanodroplets dispersed in a liquid phase: A Monte Carlo simulation study of a ternary system

This work employs semigrand canonical ensemble Monte Carlo simulations to investigate the morphology of biphasic nanodroplets suspended in a liquid phase. Using a ternary Lennard-Jones system, we explore the free energy landscapes, nucleation pathways, and thermodynamic stability of core-shell, Janus, and dumbbell configurations that arise from internal phase separation within a parent nanodroplet. Our simulations confirm that the final morphology is dictated by the balance of interfacial free energies between the two droplet components and the surrounding liquid. While a thermodynamic model based on binary interfacial energies provides general predictions, the adsorption of a third component at the liquid-liquid interface alters the interfacial free energy, leading to discrepancies between the model and simulation, particularly for core-shell and crescent-shell morphologies. We also observe a link between the nucleation mechanism and the resulting morphology. Nucleation occurs at higher compositions for systems that form Janus droplets compared to those that form core-shell structures. These findings highlight the limitations of macroscopic models at the nanoscale and offer a more nuanced understanding of phase transitions in nanodroplets, which is essential for the rational design of complex nanoparticles.