Molecular Dynamics Simulation Study of Solid‐Liquid Phase Transition in Water Clusters. The Effect of Cluster Size

Abstract

Solid SPC/E and TIP4P water clusters of varying sizes from 8 to 216 molecules have been studied over a temperature range from 0 to 200 K using Molecular Dynamics computer simulations. Solid‐to‐liquid phase transitions were investigated to estimate the effect of cluster size (n) on its melting temperature. Simulations demonstrate that water model geometry is crucial for description of the solid cluster phase behaviour. For solid clusters with n>24 molecules the three‐site SPC/E water model gives higher melting temperatures than the four‐site TIP4P. For smaller clusters with n<24 the situation is diametrically opposed. The analysis of the effect of cluster size on its melting temperature shows that classical liquid drop approximation is useful for both SPC/E and TIP4P clusters. In the case of three‐site SPC/E water the classical relation is valid even for as small clusters as n=12, in the case of the four‐site TIP4P model, it is valid only for n≥20.