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.