At ξ ∼ 0.5 nm, the first of the two hydroxyl groups interacts with the oxygen atoms of the hematite surface with a OH•••O distance of ∼ 1.6 Å. At ξ ∼ 0.4 nm, both hydroxyl groups are interacting with the oxygen atoms of the surface, and the PMF exhibits a local minimum. ξ ∼ 0.3 nm corresponds to the global adsorption minimum, where the --O atom of the headgroup also interacts with the surface with a --O•••Fe distance of ∼ 2.6 Å. There is a small energy barrier between the two adsorption modes related to the energy required to further approach the headgroup center of mass to the hematite surface. In this transition, the tailgroup goes from being located at the second maximum of the solvent mass density profile at 0.7-0.8 nm to being partially or completely located at the first maximum at 0.3 nm from the surface. In the case of GMS, the tailgroup at the global minimum lies flat to the surface, whereas for GMO, the half of the C atoms lie flat to the surface, with the remaining half pointing into the solvent layer due to the presence of the Z-alkene group.