  Heat capacity curves as functions of temperature were calculated using Monte
Carlo methods for the series of Ar_{13-n}Kr_n clusters (0 <= n <= 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 multi-component
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 energy isomer had an icosahedral-like symmetry typical of homogeneous
thirteen-atom rare gas clusters, with an Ar atom being the central atom.
