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

## TL;DR

This study explores how the left- and right-handed forms of carvone affect their ability to prevent metal corrosion, finding that the right-handed form is more effective.

## Contribution

The first investigation of how molecular chirality influences corrosion inhibition by carvone isomers using DFTB simulations.

## Key findings

- The (S)-(+) isomer of carvone shows greater corrosion inhibition due to more favorable adsorption energies.
- Adsorption on α-Fe(110) is driven by van der Waals, electrostatic, and chemical interactions.
- The protective layer remains stable even when solvent water molecules are included in simulations.

## Abstract

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.