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 Tm(D) functions for metallic nanoparticles, nanostructures, and nanoparticles embedded in a coherent or incoherent interface. Tm(D) functions are determined by the sign of γss, fss (or γsl and fsl), and D0 as caused by the change of interface environments. We found that there is TCIm(D) > TNSm(D) > TIIm(D) > TNPsm(D) for Ag nanocrystals within different interfaces. Moreover, for a given size, Tm(D)/Tm(∞) decreases with the reduction of γss/fss 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 TNPsm(D)/Tm(∞) < TIIm(D)/Tm(∞) < TNSm(D)/Tm(∞), which is in agreement with the relation of γNPssl/fNPssl < γIIss/fIIss < γNSss/fNSss. By analyzing the γss(D) (or γsl(D)), fss(D) (or fsl(D)) and γss(D)/fss(D) (or γsl(D)/fsl(D)) functions of Ag nanocrystals and comparing with their Tm(D) functions, it is found that there is a high consistency between the variation of γss(D)/fss(D) (γsl(D)/fsl(D)) and Tm(D)/Tm, which reveals that the size dependence of Tm(D)/Tm is determined by γss(D)/fss(D) (or γsl(D)/fsl(D)). Our predictions show a good agreement with the available theoretical and experimental results.