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 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, 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 TNPsm(D)/T_m(∞) < TIIm(D)/T_m(∞) < TNSm(D)/T_m(∞), which is in agreement with the relation of γNPssl/fNPssl < γIIss/fIIss < γNSss/fNSss. 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 of 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.