To address the overestimation of W sl , we introduced a new solid-liquid potential, ClayFF 0.5ε O , which halved the value of ε O in ClayFF for the solid-liquid LJ interactions (ε O = 0.0777 kcal mol -1 ), whilst leaving the remaining parameters unchanged. We decided to change the ε O parameter because the ε F e parameter of ClayFF was already so small (ε F e = 9.0 × 10 -6 ) that reducing it further would likely have a negligible impact on the W sl . We then recalculated θ and W sl with this new potential. The results of these simulations are detailed To achieve this agreement with W sl from contact angle experiments, 105 we reduced the strength of the O surf -C f luid and O surf -H f luid LJ interactions, which have been carefully parameterised (at least for O f luid -C f luid and O f luid -H f luid ) in the molecular force-field. This raises the question as to whether our system is fully representative of the state of solidliquid interface in the contact angle experiments. Experimental studies have shown that surface hydration and hydroxylation can occur on hematite surfaces at relative humidities as low as 0.1 %. The relative humidity was not reported for the contact angle experiments used to calculate the work of adhesion. 105 However, since no controlled atmosphere was used, it is very likely that an interfacial hydroxyl and/or water layer was present between the hematite and the PAO4 in the contact angle experiments. The presence of these layers could screen the interactions between the Fe 2 O 3 and PAO4, reducing adhesive forces with respect