The transition between the hexagonal ice I and the liq-uid state has been previously studied using the ST2 potential to describe the pair interaction between water molecules, II An additional external wall potential has been used to keep the cluster bounded in size and location, and to keep the droplet compressed. The ST2 potential was chosen to model the water because it has the following advantages: (i.) it is a simple potential form whose properties have been well char-acterized by extensive simulations; (ii.) it treats the water molecule as a rigid asymmetric rotor; (iii.) it realistically ac-counts for hydrogen bonding; (iv.) it successfully reproduces the thermodynamic anomalies of bulk liquid water. 2, 1 1 The wall potential was chosen to have the following form: U (r; ) = cosh(ar; )I cosh(ar 0)' (2.1) where r; is the distance of the center of mass of the ith mole-cule from the origin. The parameter a was chosen to be 2 A -I and U as written is given in kcal/mol. For the high pressure melting ro was chosen to be 12 A (our previous study used the value 20 A). This choice for ro produces a