Thermal Stability of Au@Pd Core/Shell Nanoparticles with different Hollow Au Cores : Molecular Dynamics study

Abstract

The thermal behaviors of the core/shell spherical Au@Pd nanoparticles (NPs) with different hollow Au core sizes for the diameter of 7nm and 8nm NPs were first investigated by molecular dynamics (MD) simulations. Size effect on their thermodynamic stability related to the melting behavior was examined by caloric curves, the specific heat capacity, self-diffusion coefficients and total radial distribution functions under continuous heating process. The predicted results for four hollow NPs were evaluated by comparing with those obtained for the solid core-shell Au0.42Pd0.58 and Au0.63Pd0.37 NPs. The hollow Au@Pd NPs with thin Pd shells exhibited less thermodynamic stability and smaller melting point than those of the solid ones with the same size. A two stage melting process was observed clearly for only one hollow NPs within the Pd rich compositions. The negative heat capacity occurs only at the second stage melting in hollow core-shell of Au0.34@Pd0.66 NPs. These results indicate that the composition of hollow Au@Pd NPs together with hollow size is more important than the shell thickness of NPs. Thus, an atomistic insight into the size and thermal effect on the hollow NPs has presented for the future construction of core-shell type Au@Pd nano catalysts with hollow structures.