Computational Analyses of <i>Peganum harmala</i> Alkaloids as Green Corrosion Inhibitors on Fe(110)

One of the successful techniques developed for the inhibition of metal corrosion is the utilization of phytochemicals from plant extracts as corrosion inhibitors. Theoretical studies are utilized to predict how organic components behave on metal surfaces and can pave the way for the development and synthesis of innovative, efficient corrosion inhibitors. However, atomic-level insights into the inhibition mechanisms of these green components are still needed. In this paper, the interactions of three active components found in aqueous <i>Peganum harmala</i> extract (harmol, vasicinone, and harmalol) with the Fe(110) surface are theoretically investigated using density functional theory (DFT) and atomistic molecular dynamics (MD) simulations. Several analyses and quantities related to adsorption, such as adsorption energy, partial density of states, Bader charge, charge density difference, and electron localization function, are described in detail. Both DFT calculations and MD simulations reveal that these molecules favor a lateral adsorption configuration, with π-back-donation being the dominant mechanism in their adsorption onto the Fe surface. The results indicate that the polycyclic heteroaromatic compounds significantly affect the adsorption of the molecules on the Fe surface. This highlights the fact that the effectiveness of the inhibitors is closely tied to their molecular structure.