Interfacial melting mechanism of nanocrystals determined by interfacial energy and interfacial stress.

To clarify the interface melting mechanism, a unified analytical expression was developed to describe the depression and superheating of T m ( D ) functions for metallic nanoparticles, nanostructures, and nanoparticles embedded in a coherent or incoherent interface. T m ( D ) functions are determined by the sign of γ ss , f ss (or γ sl and f sl ), and D 0 as caused by the change of interface environments. We found that there is T CIm( D ) > T NSm( D ) > T IIm( D ) > T NPsm( D ) for Ag nanocrystals within different interfaces. Moreover, for a given size, T m ( D )/ T m (∞) decreases with the reduction of γ ss / f ss for nanoparticles, nanostructures and nanoparticles embedded in incoherent interfaces, while an opposite trend occurs for the coherent interfaces. In addition, we also found that there is T NPsm( D )/ T m (∞) < T IIm( D )/ T m (∞) < T NSm( D )/ T m (∞), which is in agreement with the relation of γ NPssl/ f NPssl < γ IIss/ f IIss < γ NSss/ f NSss. By analyzing the γ ss ( D ) (or γ sl (D)), f ss (D ) (or f sl ( D )) and γ ss (D )/ f ss ( D ) (or γ sl ( D )/ f sl ( D )) functions of Ag nanocrystals and comparing with their T m ( D ) functions, it is found that there is a high consistency between the variation of γ ss ( D )/ f ss ( D ) ( γ sl ( D )/ f sl ( D )) and T m ( D )/ T m , which reveals that the size dependence o f T m ( D )/ T m is determined by γ ss ( D )/ f ss ( D ) (or γ sl ( D )/ f sl ( D )). Our predictions show a good agreement with the available theoretical and experimental results.