YANG Quan-Wen1, ZHU Ru-Zeng1, WEI Jiu-An1, WEN Yu-Hua2
1State Key Laboratory for Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080
2Department of Physics, Xiamen University, Xiamen 351005
Surface-Induced Melting of Metal Nanoclusters
YANG Quan-Wen1;ZHU Ru-Zeng1;WEI Jiu-An1;WEN Yu-Hua2
1State Key Laboratory for Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080
2Department of Physics, Xiamen University, Xiamen 351005
Abstract： We investigate the size effect on melting of metal nanoclusters by molecular dynamics simulation and thermodynamic theory based on Kofman’s melt model. By the minimization of the free energy of metal nanoclusters with respect to the thickness of the surface liquid layer, it has been found that the nanoclusters of the same metal have the same premelting temperature Tpre=T0-T0(γsv-γlv-γsl)/(ρLξ) (T0 is the melting point of bulk metal, γsv the solid--vapour interfacial free energy, γlv the liquid--vapour interfacial free energy, γsl the solid--liquid interfacial free energy, ρ the density of metal, L the latent heat of bulk metal, and ξ the characteristic length of surface-interface interaction) to be independent of the size of nanoclusters, so that the characteristic length ξ of a metal can be obtained easily by Tpre, which can be obtained by experiments or molecular dynamics (MD) simulations. The premelting temperature Tpre of Cu is obtained by MD simulations, then ξ is obtained. The melting point Tcm is further predicted by free energy analysis and is in good agreement with the result of our MD simulations. We also predict the maximum premelting-liquid width of Cu nanoclusters with various sizes and the critical size, below which there is no premelting.
2004, Vol. 21 
