Wetting transition of water on graphite: Monte Carlo simulations

We report evidence observed from molecular simulations for the first-order wetting transition of water on a solid surface. Based on the empirical potentials of SPC/E for water, the 10-4-3 van der Waals model, and a recently developed induction and multipolar potential for water and graphite, we show through a series of Monte Carlo simulations that the first-order wetting transition of water on graphite occurs at $475–480\mathrm{K}$, and the prewetting critical temperature lies in the range $505–510\mathrm{K}$. The calculated wetting transition temperature agrees quantitatively with that predicted previously using a simple model.

Figure 1

Adsorption isotherms of water on graphite from GCMC simulations and MHR, where ${\rho }^{*}$ is the reduced number density. The curves correspond to $T=510$, 505, 500, 490, 480, and $475\mathrm{K}$, from left to right.

Figure 2

Local density profiles for water adsorption on graphite as a function of reduced distance from the surface, $z^{*}=z∕{\sigma }_{\mathrm{f}}$. $T$=(a) 475, (b) 490, and (c) $510\mathrm{K}$. In (a) and (b), the values of ${\chi }^{*}$ at which the calculations were performed are indicated by the labels in the graph. In (c), profile curves are for ${\chi }^{*}=$ 0.731, 0.878, 0.892, 0.919, 0.940, 0.962, 0.977, 0.995, and 1.003, from bottom to top.

Figure 3

Film density for water on graphite at $T=490\mathrm{K}$ and ${\chi }^{*}=0.992$. Curves correspond to varying heights of the simulation cell, $H^{*}=10$, 20, 40, and 30, from left to right.