Investigation of Corrosion Inhibition and Adsorption Properties of Quinoxaline Derivatives on Metal Surfaces Through DFT and Monte Carlo Simulations

This work presents a multiscale theoretical investigation into the potential of quinoxaline derivatives (Q1–Q6) as corrosion inhibitors for various metals (Fe(110), Cu(111), and Al(110)). Employing a combined approach combining density functional theory (DFT) and Monte Carlo simulations, we explore the relationship between molecular structure, electronic properties, and adsorption behavior. Density functional theory (DFT) and molecular dynamics simulations (MDS) were used to investigate the electronic characteristics of diverse compounds. The study included key parameters including highest occupied molecular orbital energy ( E HOMO ), lowest unoccupied molecular orbital energy ( E LUMO ), energy gap ( E g ) between E LUMO and E HOMO , dipole moment, global hardness, softness ( σ ), ionization energy ( I ), electron affinity ( A ), electronegativity ( χ ), back-donation energy E b−d , global electrophilicity ( ω ), electron transfer, global nucleophilicity ( ε ), and total energy (sum of electronic and zero-point energies). These properties, alongside adsorption energies (following the trend Q6 > Q2 > Q3 > Q4 > Q5 > Q1), are used to identify promising inhibitor candidates and establish structure–property relationships governing their effectiveness. The results suggest that inhibitor efficiency increases with a decreasing energy gap between frontier orbitals. Notably, the protonated state of Q6 exhibits high reactivity, low stability, and strong adsorption, making it a potential candidate for further exploration. This comprehensive theoretical approach offers crucial insights for the conceptual development of new and powerful corrosion inhibitors.