Computational Experiments for Designing High‑Performance Oxadiazole Corrosion Inhibitors

Organic corrosion inhibitors protect steel against degradation by forming chemisorbed molecular films, with inhibition efficiency governed by the interplay between electronic structure and adsorption behaviour. This work employs density functional theory (DFT)-based computational screening [1] to design and evaluate a novel series of oxadiazole‑based inhibitors for Fe surfaces, establishing a rigorous structure–property–performance relationship. Using the recently reported high‑performance inhibitor 2‑(5‑methylthiophen‑2‑yl)‑5‑(pyridin‑3‑yl)‑1,3,4‑oxadiazole (MTPO‑3) as a structural benchmark [2], a systematic library of isomers was generated through systematic rational modification of heteroatom positions and ring connectivity. DFT calculations identified 2‑(5‑methylthiophen‑2‑yl)‑5‑(pyridin‑2‑yl)‑ 1,3,4‑ oxadiazole (MTPO‑2) as the most stable isomer, exhibiting a higher HOMO energy, lower LUMO energy, and a narrower HOMO–LUMO gap—collectively indicative of superior electronic reactivity and enhanced electron-donor capacity toward Fe. Spin‑polarised DFT calculations were subsequently employed to evaluate the adsorption energetics of MTPO-2 and MTPO-3 on Fe(100) and Fe(110) surfaces. The computed adsorption energy of MTPO-3 on Fe(110) shows close agreement with published values [2], validating the reliability of the surface adsorption model. MTPO‑2 consistently exhibited stronger adsorption across both surface facets, corroborating its superior electronic profile. These results demonstrate that DFT‑guided isomer engineering is a powerful and systematic strategy for the rational design of high-performance oxadiazole corrosion inhibitors. Full computational details and mechanistic insights will be presented at the conference.