Journal of Chemical Physics, Vol.105, No.22, 10030-10049, 1996
A Computational Study of 13-Atom Ar-Kr Cluster Heat-Capacities
Heat capacity curves as functions o f temperature were calculated using Monte Carlo methods for the series of Ar13-nKrn clusters (0 less than or equal to n less than or equal to 13). The clusters were modeled classically using pairwise additive Lennard-Jones potentials. J-walking (or jump-walking) was used to overcome convergence difficulties due to quasiergodicity present in the solid-liquid transition regions, as well as in the very low temperature regions where heat capacity anomalies arising from permutational isomers were observed. Substantial discrepancies between the J-walking results and the results obtained using standard Metropolis Monte Carlo methods were found. Results obtained using the atom-exchange method, another Monte Carlo variant designed for multicomponent systems, were mostly similar to the J-walker results. Quench studies were also done to investigate the clusters’ potential energy surfaces; in each case, the lowest isomer had an icosahedral-like symmetry typical of homogeneous 13-atom rare gas clusters, with an Ar atom being the central atom.
Keywords:LENNARD-JONES CLUSTERS;RARE-GAS HETEROCLUSTERS;MONTE-CARLO SIMULATIONS;SMALL METAL-CLUSTERS;NORMAL MODE ANALYSIS;ARGON CLUSTERS;THERMODYNAMIC PROPERTIES;VANDERWAALS CLUSTERS;PHASE-TRANSITIONS;MAGIC NUMBERS