Phase transitions in large atomic clusters. Computer modeling

A modified Monte Carlo method was developed that mimics phase transitions in atomic clusters and implemented to obtain, for the first time via computer modeling, size dependencies of argon cluster properties in the mesoscopic size range from 2000 to 12000 atoms and in a temperature range of 20–80 K. Thermodynamic functions were calculated and the equilibrium phase state was found for these temperatures. Two criteria, such as melting temperature and mean interatomic distance, show in accordance that cluster thermal properties become close to that of a macroscopic body at cluster size Ncl ≈ 10000 atoms. The proposed method allows one to avoid the exponential growth of the required number of Monte Carlo steps with cluster size, thus exponentially diminishing the required simulation time.