DFTB Study of Corrosion Inhibitory Properties of (R)‑(-) and (S)‑(+)-Carvone Isomers

Using density functional tight binding (DFTB) calculations, we investigate, for the first time, how molecular chirality modulates the corrosion-inhibition behavior of carvone isomers, the R- and S-isomers, to evaluate their potential as green organic inhibitors. We assess the isomers with respect to their interactions with the α-Fe(110) surface under various environmental conditions. Adsorption energies and geometries, density of states, and charge distribution are analyzed to describe the adsorption-driven inhibition mechanism. The adsorption of the isomers on the α-Fe(110) surface is driven by van der Waals, electrostatic, and chemical interactions. The results reveal that adsorption is governed by a combination of chemisorption and physisorption, mediated by the carbonyl oxygen and π-electron system of the cyclohex-2-enone ring. The (S)-(+) isomer exhibits a greater corrosion inhibition capacity due to more favorable adsorption energies. The explicit inclusion of solvent water molecules during the simulations does not destabilize the inhibitor-surface interaction. These results indicate that the protective layer remains stable under hydrated conditions. These results suggest that (R)-(-) and (S)-(+)-carvone are promising candidates for sustainable corrosion inhibitors, with (S)-(+)-carvone exhibiting superior adsorption stability.