Self-Adaptive Layering Structure of Nanoconfined Fe–Ni\nLiquids: Origin of the Liquid–Liquid Phase Transition

Metallic liquids\nunder confinement exhibit different properties\ncompared to those of their corresponding bulk phases, such as miscibility,\ndiffusion, and phase transitions. Unfortunately, the challenges in\nexperimentally characterizing Fe–Ni liquids at the nanoscale\nand the high cost of first-principles simulations hindered the atom-level\nunderstanding that is necessary for controlling Fe–Ni liquids.\nHere, we report a comprehensive molecular dynamics study of the liquid\nFe–Ni alloy confined within nanoslits. Driven by the slit size,\nthe confined Fe–Ni liquid experiences the liquid–liquid\nphase transition (LLPT) that is characterized by layering transitions.\nInterestingly, during the LLPT, a transition liquid phase appears,\nseparating two layering phases, which is accompanied by abnormal variations\nin density, potential energy, and pressure perpendicular to the wall.\nThe Voronoi cluster analysis reveals a self-adaptive local structural\nevolution in confined Fe–Ni liquids during the LLPT. The effect\nof temperature, pressure, and composition on the LLPT is investigated.\nBased on the pressure-confinement phase diagram, the LLPT is mainly\ninduced by confinement under high pressure, while under low pressure,\nthe LLPT is mainly pressure-driven. Our research will stimulate more\ninterest in the phase transition under confinement in a metallic system.