Computational Insights into Corrosion Inhibition Efficiency of 5-Bromothiophene-2-Carbaldehyde: A DFT and Monte Carlo Simulation Approach

This study investigates the corrosion inhibition efficiency of 5-Bromothiophene-2-Carbaldehyde (5-BTCA) using a combined Density Functional Theory (DFT) and Monte Carlo (MC) simulation approach. Quantum chemical calculations performed with Gaussian 16 evaluated the structural, electronic, and vibrational properties of 5-BTCA in the gas phase and in DMSO, ethanol, and water. Results reveal minimal solvent impact on molecular geometry but significant influence on vibrational frequencies, especially in polar solvents. The DFT calculations revealed 5-BTCA as a strong electron donor with a lower HOMO-LUMO energy gap (4.551 eV in H2O and 4.567 eV in ethanol), which signifies greater reactivity and absorptivity in the aqueous environment. The chemical potential (μ = -4.633 eV in H2O) and electrophilicity index (ω = 4.714 in H2O) indicated the molecule to be involved in strong interactions with metal surfaces. Natural Bond Orbital (NBO) analysis showed stable donor-acceptor interactions and solvent effects on π-bond delocalization. MC simulations, conducted on the Fe(110) surface in an acidic environment, demonstrate strong spontaneous adsorption of both protonated and unprotonated 5-BTCA, with the protonated form exhibiting slightly higher adsorption energy, indicating superior inhibition stability.