| Supersonic cold gas spray is a new coating process which has many good attributes and it has attracted attentions from scholars in and abroad. But as a newly-developed technology, it is short of perfect theory and the quality and the efficiency of spray should be improved. And what's more, it has not been carried out in practical project although it can be applied to nanometer-sized particle spray. The"cold"in the cold gas spray means the particles adhere to the surface of substrate under the situation that don't melt down, Methods used in molecular dynamics simulation of the surface sediments, and the number of particles is closely related to the melting point of spraying particles is essential. Therefore, using molecular dynamics simulation to explore the micro-nano-clusters under the melting points, is of great academic value and engineering background.We use the molecular dynamic simulation method to simulate the melting process of the nanometer-sized Au clusters. Four methods are adopted to analyze the results of simulate, they are the pair correlation function,potential-temperature,mean square displacement and key analysis. We make a comparison with these four methods, we can see the cluster changes from order to disorder obviously through the pair correlation function, but can't get the melting point exactly. Potential-temperature method is build on a microcosmic mechanism that the distance among atoms can have a leap near the melting point, through this method we can get melting point much more exactly. Mean square displacement can get melting point by calculate the square distance of all atoms, can be more accurate to give a scope of melting point. Key analysis, in the process of changing from solid to liquid, the microcosmic configuration of the cluster have a big change, so the change point is the melting point. At last, we find Potential-temperature method, MSD and key type analytical method can accord with the theories calculation numerical value.
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