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Two methods for including the effects of electron correlation on the electron density distributions of molecules are compared. Second-order Mo/ller–Plesset perturbation theory (MP2) is shown to give electron density distributions in good qualitative agreement with much more time-consuming configuration interaction calculations. The latter include all single and double substitutions from the Hartree–Fock reference configuration. The two methods are compared by means of difference density maps calculated with large basis sets for a few representative molecules. From an analysis of the relative importance of single and double substitutions, it is shown that double substitutions are dominant near nuclei, but in other regions of space the single substitutions are more important. The MP2 method is shown to provide a practical method for calculating the correlation corrections to the electron density distributions of molecules of intermediate size.

A hydrophilic copolymer (MA‐APEA) containing carboxylic acid group and ethylene oxide group is synthesized from maleic anhydride (MA) and allyloxy polyethoxy carboxylic acid (APEA) in free radical polymerization and its structure is characterized using FT‐IR, 1H nuclear magnetic resonance spectrometer and gel permeation chromatographic techniques. Seven polymer solutions with different degrees of deprotonation are prepared by adding caustic solution to the polymer solution. Effects of the degree of deprotonation of the polymer on curbing calcium scale and the corrosion inhibition of low carbon steel are studied. Influences of the operating conditions on inhibition against CaCO3 scale by the polymer with different degrees of deprotonation are also investigated. Effects of the degree of deprotonation on CaCO3 deposits/precipitate are analyzed using scanning electronic microscope and X‐ray diffraction. The results show that different degrees of deprotonation of the polymer have different influences on different calcium scale and corrosion inhibition of low carbon steel. The performance of the polymer to withstand high alkalinity and high hardness and high temperature decreases with increase in the degree of deprotonation. The change in the degree of deprotonation influences the conversion of aragonite and vaterite to calcite, and hardly impacts the crystal morphology of CaCO3 crystals. MA‐APEA has proven to be an excellent calcium scale inhibitor.

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Polymer scale inhibitors have been widely used to reduce the loss caused by mineral scaling in circulating cooling water systems. In this article, four maleic acid‐based copolymers [hydrolyzed polymaleic anhydride (HPMA)‐AEO] containing different fatty alcohol polyoxyethylene ether (such as AEO‐9, AEO‐10, AEO‐15, and AEO‐20) are prepared by the way of free‐radical copolymerization and characterized using Fourier transform infrared (FTIR), 1H NMR, and gel permeation chromatographic (GPC) techniques. The effects of HPMA‐AEO on CaCO3 scale are studied in several aspects (such as dose, Ca2+ concentration, temperature, inhibition time, pH, the ratio of EO:carboxyl, and the relative supersaturation of CaCO3 solution) by static experiments. The CaCO3 scaling process with dosing of HPMA‐AEO‐9 is investigated under dynamic tests. CaCO3 deposits and precipitate in the presence of HPMA‐AEO‐9 are analyzed using scanning electronic microscope (SEM) and X‐ray diffraction (XRD). The results show that the performance of HPMA‐AEO against CaCO3 scale highly depends upon the ratio of EO:carboxyl; the introduction of AEO group can significantly improve the performance of HPMA‐AEO to tolerate high alkalinity, high hardness, and high temperature; the presence of HPMA‐AEO‐9 can obviously affect the CaCO3 scaling process on the tube wall through interfering with nucleation process and crystal growth process and significantly alter the surface morphology and crystal form of CaCO3 deposits. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47470