A state-of-the-art approach to addressing the missing ingredients of molecular modeling

More environmentally friendly organic molecules are gradually replacing the toxic inorganic ones used in corrosion inhibition (CI). Molecular modeling approaches can help to unveil their acting mechanisms, paving the way for a rational design of novel inhibitors. Nonetheless, CI modeling frequently neglects crucial aspects such as the solvent and voltage effects. We present a state-of-the-art approach to tackle that problem by combining the non-equilibrium Green's functions (NEGF) formalism with the quantum mechanics/molecular mechanics (QM/MM) method to include the voltage effects while fully accounting for the solvent with atomic resolution, but at an affordable computational cost, as implemented in the SIESTA code.

We apply this approach to study the interaction between mercaptobenzimidazole (MBI) and cooper under different concentrations. Our results show that the stability of the adsorbed layer increases as we increase the coverage, forming a self-assembled monolayer. We also demonstrate that the charge redistribution due to the voltage applied to the metallic substrate leads to significant changes, also affecting the structural properties of the solvent (water). In summary, the proposed NEGF-QM/MM approach presented here might represent a significant step forward in modeling electrochemistry, which we demonstrate can be successfully applied in CI.