A Study of Low Temperature Heat Capacity Anomalies in Bimetallic Alloy Clusters using J-Walking Monte Carlo Methods

摘要

Heat capacities are calculated as a function of temperature for bimetallic clusters composed of six palladium and seven nickel atoms using Monte Carlo techniques both with and without J-walking. By applying a simulated annealing strategy, the minimum energy configurations at 0 K are identified for a series of interatomic interaction strengths. A significant dependence of the spatial arrangement of atoms on the strength of the Pd-Ni interaction is observed. Calculations of the heat capacity as a function of temperature show the presence of a “melting” coexistence region similar to that observed in pure clusters. For the alloy clusters, low temperature heat capacity anomalies are observed arising from isomerizations that are reminiscent of order-disorder transitions known to occur in some bulk alloy materials. These low temperature heat capacity anomalies are observable only when the J-walking algorithm is used.