The pressure was controlled during the equilibration phase by applying a constant force to the outer layer of atoms in the top wall. After equilibration, the outer layers of both hematite slabs were fixed in place for the subsequent PMF production simulations. At the start of the equilibration phase, the velocities of the solvent, OFM and non-fixed hematite atoms were initialized using with a Gaussian distribution of velocities corresponding to a temperature of 300 K. The temperature was then controlled using the Nosè-Hoover thermostat with a time relaxation constant of 0.1 ps. The thermostat was applied to all of the non-fixed atoms.