Evolution of the Ni-Al Janus-like clusters under the impacts of low-energy Ar and Ar13 projectiles

Abstract

The evolution of free 390-atom Janus-like Ni-Al clusters along 100 and 500 ps under impacts of up to 1.0 keV Ar and Ar13 projectiles is simulated by the classical molecular dynamics method. The initial metastable Janus-like clusters have two mono-component parts, equal in number of atoms, with a small spatial overlap. After an impact of the projectiles and rapid expansions accompanied by sputtering at a high-temperature spike for less than 0.5 ps, where critically different kinetics are found in the cases of Ar1 and Ar13 projectiles, the resulting Ni-Al clusters gradually evolve due to exothermic mixing of the components and the tendency of surface segregation of Al atoms. The surface enrichment by Al atoms after 500 ps is clearly seen in the case of Ar1 impacts whereas at Ar13 impacts with the energies above 100 eV this tendency is masked by intense sputtering, which includes both collisional and long-term thermal contributions, with a large preferential yield of Al atoms.