DFT, Monte Carlo and molecular dynamics simulations for the prediction of corrosion inhibition efficiency of novel pyrazolylnucleosides on Cu(111) surface in acidic media
Authors: Kaltrina Jusufi
Virinder S Parmar
Mustapha Ait El Had
Avni Berisha
Christophe Len
Souad El Issami
Rachid Oukhrib
Hicham Abou Oualid
Jeton Halili
Fatmah Ali Asmary
Youness Abdellaoui
Hassan Bourzi
Journal: Scientific Reports (2021)
Discipline: Multidisciplinary
Keywords: pyrazolylnucleosides; corrosion inhibition; DFT calculations; molecular orbital energies; chemical properties
Affiliations: Apply Chemistry-Physic Team, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco., Faculty of Engineering, Environmental Engineering Department, Autonomous University of Yucatan, Mérida, Mexico., Department of Chemistry, Faculty of Natural and Mathematics Science, University of Prishtina, 10000, Pristina, Kosovo., Laboratory of Biotechnology, Materials and Environment, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco., Green Enenrgy Park, IRESEN, Ben Guerir, Morocco., Laboratoire de Chimie Biomoléculaire, substances naturelles et Réactivité (URAC 16), Faculté des Sciences Semlalia, Université Cadi Ayyad, B.P. 2390, Marrakech, Morocco., Laboratoire de Chimie Bioorganique et Macromoléculaire, Faculty of Sciences and Technics Marrakech (FSTMG), Université Cadi Ayyad, Marrakech, Morocco., Chemistry Department, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia., Department of Chemistry and Environmental Science, Medgar Evers College, The City University of New York, 1638 Bedford Avenue, Brooklyn, NY, 11225, USA., Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Life and Health Sciences, 11 rue Pierre et Marie Curie, 75005, Paris, France. .

Abstract:  Five novel pyrazolylnucleosides have been evaluated theoretically for their corrosion inhibition efficiency on the Cu(111) surface in acidic media. DFT calculations were carried out to exhibit the intrinsic properties such as lowest unoccupied (ELUMO) and highest occupied (EHOMO) molecular orbital energies, as well as energy gap (∆E), chemical hardness (η), chemical softness (σ), electronegativity (χ), electrophilicity (ω) and nucleophilicity (ε). The theoretical FT-IR spectra were recorded to indicate the presence of the specific bonds in the studied molecules. The surface interactions between the inhibitor molecules and the metal surface were investigated using molecular dynamics simulations and Monte Carlo (MC) simulations. As a result, we have found that the inhibitor pyrazolylnucleosides 5a-e have strong interactions with Cu(111) surface, and therefore have excellent predictive inhibition power against copper corrosion. 

Retracted: No

PubPeer comments:
 The molecular simulations are of very low quality, most of the quantities reported are not converged at all. Figure 6 shows  the vibrational spectra using an FT-IR spectrometer , so we have to assume that it s an experiment. No details are available on the conditions of the experiment, what spectrometer was used, where the compounds were obtained from, etc. The abstracts contradicts this:  The theoretical FT-IR spectra were recorded , but there is nothing in the methods section that explains how those spectra are calculated (not recorded). Figure 13 is  RDF O (a) and RDF N (b) of the pyrazolylnucleosides 5au2013e on the Cu(111) surface in solution : ![file] Because partial RDF are functions between two types of atoms, I think those are Cu-O and Cu-N, but that s never stated. Given the planar geometry of the Cu surface, the quantity that should be calculated is not an RDF but an axial distribution along the normal axis, which would give clearer indications. But most of all, those RDF are not converged at all, the statistical noise is 100% of the curve value, meaning the calculation was not done properly: either the simulation is too short, or the binning is too thin. There appears to be some substructure as well, which is not discussed or analysed at all. Figure 12 shows the Monte Carlo simulations of annealing. Very little information is available in the methods, and the only information given contradicts the figure: ![file]  MC calculations were realized by applying five cycles (2000 steps in each cycle) of simulated annealing. The figure indicates it s 20,000 cycles, not 2,000. The temperature (or kinetic energy) curves are not given and the methods do not say between what temperatures the annealing was done. The methods do not say what Monte Carlo moves were performed, with what probability, or anything else. Whether it s 2,000 or 20,000 steps per cycle, it is probably too short anyway for statistical sampling, given the number of degrees of freedom involved. The authors claim, in the text and in figure 14, that chemisorption occurs: ![file] The only justification given in the text is:  Knowing that the peak between 1 and 3.5 u00c5 corresponds to chemisorption and that physisorption is associated with peaks greater than 3.5 u00c5 , and a reference to ref 24. (which does not state anything of the sort). The difference between chemisorption and physisorption depends on the formation of chemical bonds. Given that the authors used classical molecular dynamics, there are no chemical bonds formed here with the surface, and the phenomenon observed is necessarily physisorption based on weaker dispersive interactions. There can be no chemisorption in the simulations the authors have performed. ,