Atomic Composition and Structure Evolution of the Solid-Liquid Boundary in Al-Si System During Interfacial Diffusion and Contact Melting

The process of diffusion mixing at the aluminum-silicon interface in the case of two, four, seven, and ten atomic aluminum monolayers on the silicon (111) surface has been studied. The investigations were performed by the molecular dynamics simulations method using Large-scale Atomic/Molecular Massively Parallel Simulator package. Concentration and density profiles at the phase interface were analyzed to investigate the kinetics of mixing. The formation of a transient diffusion layer at the boundary of the liquid and crystalline phases is established. The melting of the phase interface was explained in the framework of the theory of contact melting. It is shown that diffusion mixing, which precedes contact melting, occurs at the level of atomic blocks (clusters), i.e. we can talk about the island nature of contact melting at the initial stage. The diffusion process was analyzed based on the theory of free volume in liquids.