MOLECULAR MODELLING AND DYNAMIC SIMULATION OF SOME CORROSION INHIBITORS IN ACIDIC MEDIUM
MOLECULAR MODELLING AND DYNAMIC SIMULATION OF SOME CORROSION INHIBITORS IN ACIDIC MEDIUM
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Date
2018-11
Authors
BELLO, Abdullahi Umar
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Abstract
The corrosion inhibition performance of amino acids, imidazole and triazole derivatives in an aqueous acidic medium on steel surfaces have been investigated by the quantum chemical calculation, QSAR analysis, and molecular dynamics (MD) simulation methods. Density functional theory (B3LYP/6-31G*) quantum chemical calculation method was used to find the optimized geometry of the studied inhibitors. Quantum chemical parameters such as energy of the highest occupied molecular orbital (E-HOMO), the energy of the lowest unoccupied molecular orbital (E-LUMO), energy band gap ΔE, Dipole Moment, electrophilicity index (𝜔), chemical softness (σ), chemical hardness (η) and fraction of electron transfer from the inhibitors molecule to the metallic surface (ΔN) have been calculated and well discussed. Additionally, a linear quantitative structure-activity relationship (QSAR) model was built by Genetic Function Approximation (GFA) method to run the regression analysis and establish a correlation between the computed descriptors and the experimental corrosion inhibition efficiencies which were used to predict the corrosion inhibition efficiencies of the studied inhibitors. The prediction of corrosion efficiencies of these inhibitors nicely matched the experimental measurements. The correlation parameters obtained for the best model in each of the three series are the squared correlation coefficients (R2) of 0.871, 0.942 and 0.862, adjusted squared correlation coefficients (R2adj) value of 0.818, 0.908 and 0.822, Leave one out (LOO) cross-validation coefficients (Q2) value of 0.750, 0.795 and 0.706, the external validations (R2pred) of 0.857, 0.983 and 0.835. These indicate that the generated models were excellent for verifying with internal and external validation parameters. Furthermore, molecular dynamics simulation is applied to search the best adorable adsorption configuration of inhibitor over Fe (1 1 0) surface. It is further confirmed by the MD simulations that adsorption of the inhibitor molecules on the metallic surfaces mainly occurred by chemical adsorption phenomenon. Thus, Quantum chemical studies, QSAR analysis along with MD simulation may be very powerful tool for the rational designing of several promising corrosion inhibitors and in prediction of their inhibition efficiencies.
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A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF SCIENCE DEGREE IN PHYSICAL CHEMISTRY DEPARTMENT OF CHEMISTRY, FACULTY OF PHYSICAL SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
MOLECULAR MODELLING,, DYNAMIC SIMULATION,, CORROSION INHIBITORS,, ACIDIC MEDIUM