Thermodynamics of small nickel clusters

The thermal stabilities and dynamics of small nickel clusters consisting of 7 to 23 atoms have been studied extensively by a molecular dynamics method based on a tight-binding many-body potential. Physical properties such as the caloric curve, melting temperature, and bond-length fluctuations are computed. The simulation indicates that the clusters undergo solid-liquid phase change with the increase in internal energy. The melting temperature is found to be a non-monotonic function of cluster size with some clusters exhibiting pre-melting behaviour. Considerable depression in the melting point of small clusters has been observed - the highest melting temperature for small clusters is found to be almost half the value for the bulk nickel. The results are discussed in the light of recent nanocalorimetric experiments on small finite particles.