Structural properties of spherical Cu/Ni nanoparticles

Abstract

While Cu/Ni bulk alloys—partially in the presence of flat surfaces—have been extensively studied, less is known about the properties of Cu/Ni nanoparticles. In the present study we employ a combined Molecular-Dynamics/Metropolis-Monte-Carlo (MD/MMC) simulation approach to analyze equilibrium segregation profiles in Cu/Ni clusters. Special emphasis is put on the relative stability of different segregation patterns and the feasibility of technically meaningful core-shell (CS) nanocrystals. We show that, although the bulk system exhibits a miscibility gap below 630 K, spherical symmetric CS nanoparticles will not form even at low temperatures, where the clusters rather adopt a highly ordered state with janus-like core structure and a Cu surface segregation monolayer atop of Ni, thereby minimizing atomic level stresses. Our simulations, performed for various particle sizes, temperatures and cross checked by using different semiempirical potentials challenge existing theoretical models and shed new light on the energy landscape of this nanoscaled system.