Size Dependence of Atomic Cluster Properties in Mesoscopic Range (Monte Carlo Modeling)

A modified Monte Carlo method was developed that mimics phase transitionss in atomic clusters and implemented to obtain for the first time via computer modeling size dependencies of an argon cluster properties in the mesoscopic size range from 2000 to 12000 atoms and in temperature range of 20-80K. Thermodynamics functions were calculated and equilibrium phase state found for these temperatures. It was shown that phase transition between solid and liquid states of an argon cluster of such size occurs abruptly and the liquid and solid states practically do not coexist, in contrast to clusters of significantly smaller sizes where the phase transition is blurred. Three criteria, such as melting temperature, mean atom displacement and mean cluster volume fluctuations show in accordance that cluster thermal properties become close to that of macroscopic body at cluster size about 10000 atoms