Modeling the melting temperature, melting entropy and melting enthalpy of freestanding metallic nanoparticles

Abstract To reveal the variation tendency of melting temperature Tm, melting entropy Sm and melting enthalpy Hm in nanoscale and the physical origin is of benefit for the understanding of the melting behavior of nanoparticles (NPs), which is critical for the design of nanodevices. In this work, a simple thermodynamic model without any adjustable parameters is proposed to predict the size dependence of Tm(D), Sm(D) and Hm(D) of metallic NPs where D denotes size. The results show that Tm(D), Sm(D) and Hm(D) functions all drop with decreasing size. The size dependence of these functions is predominated by the ratio of solid-liquid interface energy γsl and solid-liquid interface stress fsl or γsl/fsl. We find that γsl(D) exhibit much more reduction than fsl(D) when D decreases, and the difference in the size dependence of γsl(D) and fsl(D) on D is the origin of abrupt decrease of Tm(D) when D below 10 nm. The good agreement between the model prediction and the available experimental data and the results of molecular dynamics simulations, as well as other theoretical models confirms the validity of this work.