Theoretical study of the melting of aluminum clusters

The melting of Al clusters in the size range 49N62 has been studied by computer simulation in order to help interpret recent experimental results in this size range. Two model interatomic potentials are used: a Gupta potential and a glue potential which favor icosahedral and polytetrahedral structures, respectively. The glue potential exhibits a smooth relatively featureless heat capacity curve for all sizes except for $N=54$ and $N=55$, sizes at which icosahedral structures are favored over the polytetrahedral. Gupta heat capacity curves, instead, show a well-defined peak that is indicative of a first-order-like transition. The differences between the two models reflect the different ground-state structures, and neither potential is able to reproduce or explain the experimentally observed size dependence of the melting transition, hence suggesting that the experimental structures are unlikely to be icosahedral or polytetrahedral.