Theoretical studies of some sulphonamides as corrosion inhibitors for mild steel in acidic medium

Density functional theory (DFT) at the B3LYP/6‐31G (d,p) and BP86/CEP‐31G* basis set levels and ab initio calculations using the RHF/6‐31G (d,p) methods were performed on four sulfonamides (namely sulfaacetamide (SAM), sulfapyridine (SPY), sulfamerazine (SMR), and sulfathiazole (STI)) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was SMR > SPY > STI > SAM which corresponded with the order of most of the calculated quantum chemical parameters namely E_HOMO (highest occupied molecular orbital energy), E_LUMO (lowest unoccupied molecular orbital energy), the energy gap (ΔE), the Mulliken charges on the C, O, N, S atoms, hardness (η), softness (S), polarizability (α), dipole moment (μ), total energy change (ΔE_T), electrophilicity (ω), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), and the fraction of electrons transferred (ΔN). Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the sulfonamides studied. The results showed that the %IE of the sulfonamides was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the sulfonamides studied was found to be close to their experimental corrosion inhibition efficiencies. The experimental data obtained fits the Langmuir adsorption isotherm. The negative sign of the E_HOMO values and other thermodynamic parameters obtained indicates that the data obtained supports physical adsorption mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Use of HPHT Autoclave to Determine Corrosion Inhibition Effect of Poly（methyl methacrylate-co-N-vinyl-2-pyrrolidone） on Carbon Steels in 3.5% NaCl Solution Saturated with CO2

The influence of poly(methylmethacrylate-co-N-vinyl-2-pyrrolidone), P(MMA-co-VP), on corrosion of carbon steels(J55, N80, P110 SS and C110 steels) in 3.5 wt% NaCl solution saturated with CO2 was evaluated using static high pressure and high temperature(HPHT) autoclave. The surface was further evaluated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and contact angle measurements. Quantum chemical calculations have been used to evaluate the structural, electronic and reactivity parameters of the inhibitor on the steels surface. SEM, XRD and contact angle measurement studies reveal that the surface of metals are quite unaffected after use of inhibitor in 3.5% NaCl solution saturated with CO2.     

The centrifugally decoupled exponential distorted wave (CDEDW) approximation for the calculation of rotationally inelastic molecular collision cross se

A new approximate method is presented for the rapid calculation of rotationally inelastic molecular collision cross sections. The method is called the centrifugally decoupled exponential distorted wave (CDEDW) approximation and involves the combination of two well known approximations. The first approximation is the neglect of the off-diagonal coupling terms which arise from the orbital angular momentum operator in the coupled differential equations in the body-fixed axis system. The second approximation is to treat the remaining coupling terms, which arise from the interaction potential, using a unitary perturbation approximation. The CDEDW method is applied to the calculation of total and partial rotationally inelastic cross sections in the ArN₂ system, and detailed comparisons are made with exact and several other types of approximate calculations. Agreement with exact calculations is good and often comparable with the coupled states and p-helicity decoupled approximations. The CDEDW method requires a similar amount of computational effort to the infinite order sudden (IOS) approximation, and we show that for the present system the CDEDW method gives more reliable results.     

Wavepacket Propagation in the Determination of Microscopic Eigenenergies: I: The Spectral Method

Examining the relationship between chemical structure and dynamics should be fundamental to the undergraduate study of microscopic systems. With this in mind wavepacket propagation, which is traditionally used in application to dynamical problems, is used here as the foundation for determining eigenenergies. The system is propagated in space and time from an initial wavepacket as in a traditional dynamical study. We then proceed to determine eigenenergies from the appearance of resonances in a spectrum of energies that is generated from the spatial projection of the wavepacket onto the initial wavepacket. Application of the spectral method is made to a classic electronic structure problem; resonances are observed at energies which match the known energy structure of the problem. Finally, the relevance of wavepacket propagation to the elucidation of structure and dynamics at the undergraduate level is discussed.     

Sensitivity analysis of experimental data

This paper examines how a number of sensitivity techniques may be adapted to deal with the analysis of real experiments. We show that the fundamental quantities in this context are the partial derivatives of model input parameters with respect to experimental observables. They appear as a consequence of the procedure used to fit the model to the experiment. These so-called experimental elementary sensitivities are then combined with the usual model elementary sensitivities to yield coefficients which relate experimental and model observables. The importance of such coefficients for the planning of experiments is, in particular, discussed. Based on a linear analysis, we also derive simple expressions (containing the experimental elementary sensitivities) for the degree of parameter deviation arising from uncertainties in and discrepancies between model and measured observables. Finally, an overview of the role of sensitivity theory in analyzing experimental data is given.