Liquid water potential well profile

The maximum of the density profiles in both phases coincides with the location of the well depth of the (9-3) LJ water-surface potential, which is at 3 A from the surface. In the quasi-2D liquid phase, one water molecule occupies about 10 A of a surface at low temperatures. This value is approximately equal to the projection of the volume occupied by a water molecule in a bulk liquid water with p = g/cm onto the surface. Arrangement of water molecules in the quasi-2D liquid phase is shown in Fig. 15. At supercooled temperatures, the surface is covered by a dense water layer, which practically does not contain holes. Upon heating from 200 to 375 K, the density of this layer decreases by about 30%, it becomes slightly less localized (see middle panel in Fig. 14), and the holes in the layer appear. However, an infinite hydrogen-bonded water network is always present in a quasi-2D liquid water (see Section 5 for further discussion on the percolation of hydration water). 

Once the water profile has been constructed by adjusting this softness, it remains to choose the bubble-ion potentials. In fact, is it really necessary to impose such potentials. Is it not sufficient to let the ions respond to the imposed water profile. Indeed, in principle, since the ions are very well solvated in the liquid phase, they are not happy to go inside the bubble where there are no more water molecules. The chemical potential of the salt should be uniform so, without imposing any excluded volume constraint for the ions, one expects that the concentration in the gas phase, equal to the (low) activity in the liquid phase, will spontaneously be very small and negligible. In practice, unfortunately, HNC ionic profiles present high density values inside the bubble without any ionic constraint, so high that, in fact, the HNC has no solution for the interface system Figure 10 illustrates this HNC difficulty where the same soft potential [Eq. (12)] is offered to the ions but with a slightly lower bubble radius, R = 19 A, than... 

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