Structural and magnetic properties of polyicosahedral Ni–Pt–Cu ternary nanoalloys

Abstract

In this study, a series of simulations were carried out to study the effects of size, composition and geometric structure on the structural and magnetic properties of ternary Ni–Pt–Cu nanoalloys. Different sizes and compositions were considered to compare the structural stability and magnetic behavior of Ni2Pt n Cu17-n (n = 0–17), Ni3Pt n Cu20-n (n = 0–20) and Ni4Pt n Cu22-n (n = 0–22) nanoalloy systems. We performed combinations of Gupta and density functional theory (DFT) simulations to check the validity of atomistic potentials against DFT. We calculated the excess energy to analyze the relative stability of Ni–Pt–Cu nanoalloys. The most negative excess energy values at the Gupta level are obtained in the compositions Ni2Pt5Cu12 in Ni2PtnCu17-n, Ni3Pt8Cu12 in Ni3PtnCu20-n and Ni4Pt9Cu13 in Ni4Pt n Cu22-n nanoalloys. While the most stable compositions Ni2Pt5Cu12 and Ni3Pt8Cu12 at the Gupta level do not agree with those obtained at the DFT level, the lowest energy values were obtained in the same composition Ni4Pt9Cu13 of 26-atom trimetallic nanoalloys at the Gupta and DFT levels. It was also found that most of the atoms on surface sites suffer tensile strain with substitution of Pt atoms. We have also investigated the total magnetic moments of the nanoalloys. In addition, the correlation of the local magnetic moments and charges of the atoms in these systems were discussed. It was found that total magnetic moments of trimetallic nanoalloys follow an almost linear dependence on the Pt concentration, despite the small concentration of Ni atoms and the weak magnetic properties of Pt atoms.