Model prediction of melting point for nanoparticles without considering the structure

The thermodynamic behavior of nanocrystals is different from that of corresponding bulk materials, mainly because the large surface-to-volume ratio strongly affects the chemical and physical properties of nanocrystals. Fracture bonds of surface atoms inevitably lead to instability of materials at nanoscale. From the point of view of classical thermodynamics and modern molecular dynamics, many excellent models of the size and shape dependence of the melting behavior of nanosolids have been established. However, the bond properties of a system are not clear. An integrated model based on bond number and bond strength in a system with a cubo-octahedral structure is developed to predict the size-dependent thermal characteristics of nanoparticles. Without any adjustable parameters, this model can be used to predict the melting point and cohesive energy of low-dimensional materials, suggesting that both depend on the size and on the atomic distance. The good agreement of the theoretical prediction with the experimental and molecular dynamic simulation results confirms the validity of the cubo-octahedron in describing the thermodynamic behaviors of nanoparticles even without considering their crystalline structures.