Enhanced Surface Premelting of Ni₉₀Si₁₀ Nanoparticles

Molecular dynamics simulations are used to investigate the melting of Ni₉₀Si₁₀ nanoparticles. The melting is found to originate from the surface prematurely. By means of the bond order parameter, the thickness of the surface liquid layer during surface premelting is calculated. The results show that the thickness of the liquid layer increases in a logarithmic−type manner on heating to the melting temperature, which is larger than the values of elemental Ni nanoparticles. Furthermore, the temperature range associated with the premelting of Ni₉₀Si₁₀ nanoparticles is wider. Both theory and simulations indicate that the high Si concentration of the surface liquid layer formed via surface segregation during crystallization due to Gibbs adsorption is the main reason for enhanced surface premelting. The simulations suggest that the crystallization process used to prepare samples greatly influences the melting behavior of nanoparticles.