Molecular Dynamics Simulation For The Negative Heat Capacity Of Argon Clusters

Microscopic matter problem attracts researchers' attention more and more becauseit has different rules from macroscopic one. Therefore, it needs to be studied detailed tobuild corresponding theories. In the microscopic matter, nanomatter is typical and evenmany people call it the most hopeful matter in the future. The property of nanoclusterswhose sizes are between molecules and crystals is the transition from the microscopic tothe macroscopic with the quantitative growth of particles. Studying the change ofstructures and properties of them upon melting is important to understand the process ofthe structural development and to make nanomatterial. At present, it is difficult to study itthrough experiments because experiments can not measure insular clusters, but theMolecular Dynamics Simulation becomes the ideal tool to research it .In this article, wedetailed introduce Molecular Dynamics Simulation, including potential energy functions,equations of integration, periodic boundary conditions, reduced unit and so on. Themelting process of Argon (N=108, 256, 500, 864, 1372) nanoclusters have beeninvestigated by means of microcanomical Molecular Dynamics Simulation technique. Thecurve of the potential energies and the heat capacity varying with temperature are obtained.It is found that all of these clusters have negative heat capacity around meltingtemperature. To explain the micromechanics of the negative heat capacity, we analyze theenergy of these clusters upon melting. Through comparing the melting temperature ofthem, the relation between the temperature of negative heat capacity and the size ofclusters is obtained. The study on the negative heat capacity of clusters is not only beneficial to thestudy of nanomaterials but also helpful to that of the negative heat capacity ofmacroscopic matter, which is important to understand the development of the universe andget low temperature.