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5.3 conclusions 69γ L/L ∼ 0.112 J/m 2 . This value is calculated without relaxingthe atomic positions after the cut and it corresponds tothe unrelaxed adhesion energy. If we relax the surfaces wefind the relaxed adhesion energy γ L/L (∼ 0.059 J/m 2 ). Thisvalue corresponds to a surface tension of THF σ L = 0.030N/m and it can be compared with the experimental value0.027 N/m [111].As for the C/L ′ (black curve of Figure 5.8), is found thatγ C/L ′ is about 20% lower than γ L/L . This means that thewetting layer locally reduces the adhesion of the liquid.In fact, as a result of the crystallinity of the W layer, allits molecules expose their hydrophobic methylene groupsCH 2 to the liquid and the electrostatic interactions withoxygens are reduced in average. Finally, considering theZ/C cut, the Zn-O bonds are broken during the separationprocess and γ Z/C turns out to be ∼ 0.64 J/m 2 , i.e. one orderof magnitude higher than both γ L/L and γ C/L ′.Figure 5.8.: Work of separation for C/L ′ (black) and L/L (red) cases.The y axis is normalized with respect to γ L/L .5.3 conclusionsIn conclusion, we have characterized the THF/ZnO interaction,finding that the strong interaction between thesolvent and the surface causes the presence of a wettingcrystalline (i.e. ordered) monolayer that likely persists af-