Composition and Size Dependence of Alloying in Ni–Al Nanoparticles With Icosahedral and Rhombohedral Configurations: An Atomic Simulation Study

Abstract

The surface segregation and alloying of Ni–Al nanoparticles with icosahedral and rhombohedral configurations are studied via Monte Carlo simulations based on the analytic embedded atom model. The simulation shows that the alloying between Ni and Al at nanolevel is beneficial for all the studied nanoparticles. For the Ni–Al nanoalloy with icosahedral configuration, the excess energy is negative for all the compositions. This result indicates an energetic preference for the alloying of Ni and Al. The minimum excess energy decreases with increasing nanoalloy size because of the low surface–volume ratio. The compositions of Ni corresponding to the minimum excess energy increase linearly from 51.5 to 60.5% with increasing nanoalloy size. Among all the considered icosahedra and rhombohedra at the same size, the energy of the rhombohedra at the composition of 1:1, which are arranged on B2 crystal, is the smallest. With increasing nanoparticle size, the excess energies of the icosahedra at the 3:1 composition and the rhombohedra at the 1:1 composition increase. By contrast, the excess energy of the icosahedra at the 1:3 composition decreases. The result can be attributed to the competition between the Al surface segregation and alloying between Ni and Al.