Melting behavior of the (H<inf>2</inf>O)<inf>6</inf> and (H<inf>2</inf>O)<inf>8</inf> clusters

The Monte Carlo method is used to calculate, for several commonly employed model water potentials, the potential energy and specific heat of (H2O)6 and (H2O)8. For each potential considered, (H2O)8 is found to undergo a relatively sharp melting transition, with the position of the peak in the specific heat proving to be quite sensitive to the specific model potential. For (H2O)6, on the other hand, none of the model potentials leads to a sharp solid-to-liquid transition. The different thermodynamic behavior of these two clusters can be understood in terms of the differences in the density of low-lying local minima