A DFT study of the adsorption of vanillin on Al(111) surfaces.

The corrosion-inhibiting effect of vanillin molecule (VAN) and its protonated ( VANH + ) and deprotonated ( VAND - ) forms was investigated to evaluate the relationship between molecule structures and their associated efficiencies using density functional theory (DFT). The primary objective is to establish a comprehensive understanding of the relationship between molecular structures and their corrosion-inhibiting efficiencies. Global and local reactivity descriptors based on conceptual density functional theory (DFT), including the highest occupied molecular orbital energy (E_HOMO), the lowest unoccupied molecular orbital energy (E_LUMO), energy gap (ΔE_gap), global hardness (η), global softness (σ), global electrophilicity (ω), electro-donating power ( ω - ), electro-accepting power ( ω + ), and Hirshfeld Fukui indices, have been investigated. The central aim of the present study is to elucidate the adsorption mechanism and provide a clear understanding of how these inhibitors interact with the Al(111) surface under different conditions. Molecular dynamics simulations in solid-state physics were employed to explore the adsorption mechanism of inhibitors in their neutral, protonated, and deprotonated species onto the Al(111) surface. The predicted adsorption suggests that the studied inhibitors for both parallel and perpendicular orientations decrease in the order VAND - > VAN > VANH + . The VAN molecule can adsorb on the Al(111) surface in various orientations, both parallel and perpendicular, as well as using different sides of the molecule. The parallel adsorption of VAN and VAND - inhibitors on the Al(111) surface occurs primarily due to the creation of an Al‒O bond, while the VANH + form adheres to the Al(111) surface through the formation of an Al‒C bond. Furthermore, the adsorption of the neutral VAN on the Al(111) surface is not only via the oxygen atom but also through the carbon C7 atom of the carbonyl group. [ABSTRACT FROM AUTHOR]