Study the growth mechanism of AgNi nanoparticles by surface diffusion

•This paper reveals the formation mechanism of AgNi nanoparticles from the perspective of surface diffusion and the physical causes of the clustering of surface atoms into islands during growth.•Among all the surface exchange diffusion paths defined in this study, the center exchange diffusion paths, especially CPDE, are the best when the system energy decreases after the substrate boundary atom is exchanged with an adatom.•The relative magnitude of the exchange energy barriers between hetero adsorbed atoms and atoms on the substrate surface is a major determinant of the formation of core–shell and three-layer onion-like structures and the degree of surface alloying of the nanoparticles.•In addition, the appearance of surface energy trap sites during the growth of AgShellNi Core nanoparticles leads to the diffusion of surface Ag atoms to these sites and their aggregation into Ag islands.