Melting behavior of (PdxPt1−x)n nanoclusters confined in single-walled carbon nanotubes: a molecular dynamics investigation on the effects of chirality and diameter of nanotubes, and size and composition of nanoclusters

Abstract

The effects of chirality and nanotube diameter, accompanied with size and concentration of Pd, on the melting behavior of (Pd_xPt_1−x)_n bimetallic nanoclusters (with n = 108 and 256, x_Pd = 0.3, 0.5, and 0.7) confined in SWCNTs with different sizes, diameters, and chiralities were studied by MD simulation. The effect of chirality of the nanotube is significant in such a way that nanoclusters in zigzag nanotubes have higher melting temperature and greater thermodynamic stability. The effect of diameter of the nanotube is negligible and replaces zero energy. Also, the effect of cluster size is considerable, and clusters with small sizes have lower melting temperature, decreased thermodynamic stability, and stronger interactions with the tube wall. Moreover, there is a significant effect of Pd concentration in the nanocluster, and clusters with a higher concentration of Pd have a lower melting temperature and decreased thermodynamic stability. Also, a core–shell (Pt–Pd) structure was observed for (Pd_xPt_1−x)₂₅₆ nanoclusters, which is an intrinsic property and depends only on their size, not on their environment. The other important result is an fcc to hcp-like transition near the melting temperature of the studied nanoclusters, which is not dependent on the cluster size, concentration, or its environment.