A combined QM/MM molecular dynamics simulations study of nitrate anion (NO3-) in aqueous solution

The structural and dynamical properties of NO3- in dilute aqueous solution have been investigated by means of two combined quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations, namely HF/MM and B3LYP/MM, in which the ion and its surrounding water molecules were treated at HF and B3LYP levels of accuracy, respectively, using the DZV+ basis set. On the basis of both HF and B3LYP methods, a well-defined first hydration shell of NO3- is obtainable, but the shell is quite flexible and the hydrogen-bond interactions between NO3- and water are rather weak. With respect to the detailed analysis of the geometrical arrangement and vibrations of NO3-, the experimentally observed solvent-induced symmetry breaking of the ion is well reflected. In addition, the dynamical information, i.e., the bond distortions and shifts in the corresponding bending and stretching frequencies as well as the mean residence time of water molecules surrounding the NO3- ion, clearly indicates the "structure-breaking" ability of this ion in aqueous solution. From a methodical point of view it seems that both the HF and B3LYP methods are not too different in describing this hydrated ion by means of a QM/MM simulation. However, the detailed analysis of the dynamics properties indicates a better suitability of the HF method compared to the B3LYP-DFT approach.     

A Novel Repairable Fountain Codes Scheme Based on Partial Duplication Technique

Wireless Personal Communications - Distributed storage system (DSS) is an emerging paradigm which provides reliable storage services for various source data. As the fault-tolerance scheme for DSS,...     

Side effects in electrolytic deposition of nickel–boron coatings

Russian Journal of Applied Chemistry - Some side effects arising in the course of electrolytic deposition of nickel–boron coatings in the presence of sodium decahydrodecaborate were revealed....     

Method of Modeling Optoacoustic Signals in Composites Transparent Matrix – Metal Nanoparticles

Russian Physics Journal - Method of modeling optoacoustic signals initiated by a laser pulse in composites transparent matrix – metal nanoparticles taking into account melting processes has...     

Determination of the products of the oxidative transformation of unsymmetrical dimethylhydrazine in soils by liquid chromatography/mass spectrometry

Procedures are developed on the basis of liquid chromatography/mass spectrometry for determining the transformation products of unsymmetrical dimethylhydrazine in soils: formic acid dimethylhydrazide (1-formyl-2,2-dimethylhydrazine, analytical range 0.01–20 mg/kg), 1-methyl-1,2,4-triazole (analytical range 0.05–100 mg/kg), 1,1-dimethylguanidine (analytical range 0.05–100 mg/kg), and dimethylamine (analytical range 0.25–250 mg/kg). The measurements were performed in the mode of chemical ionization under atmospheric pressure followed by the registration of positive ions corresponding to the protonated forms of the components to be determined. A version of ion chromatography was elaborated for separation. For sample pretreatment, the use of extraction with methanol (for 1-formyl-2,2-dimethylhydrazine) and ultrasonic extraction with a weakly alkaline buffer solution (for other substances) was proposed.     

Luminescence of terbium and europium ions in metal-polymer complexes based on poly(amido acids) with main-chain arylcarboxyamide groups

Poly(amido acids) with main-chain metal-binding ligands methylene-bis(anthranilic acid) and their linking fragments of a widely varied structure have been synthesized. The chemical structure of poly(amido acids) that affect the luminescence of Tb³⁺ and Eu³⁺ ions and interact with them is studied, and the mechanism of this effect is advanced.     

Measurements of the refractive index of polymethylmethacrylate behind the front of a shock wave excited by a high-current electron beam

The variation of the refractive index in polymethylmethacrylate (PMMA) behind the front of a shock wave excited by a high-current electron beam is investigated. The values of refractive index in a pressure range of 2 and 4 GPa are determined from the deviation of the diagnostic laser beam. The results are compared with the available data for shock compression of PMMA.     

Effect of defect structure of lanthanum manganite on oxygen exchange kinetics and diffusion

The method of oxygen isotopic exchange was used to study the oxygen exchange kinetics and diffusion in the LaMnO_{3 + δ} oxide at the temperatures of 600–850°C and in the range of oxygen pressures of 133.3–9332.4 Pa. The rate of interface exchange and diffusion coefficient of oxygen are much lower in the case of LaMnO_{3 + δ} as compared to LaCoO_{3 − δ}, which may be due to the different defect structure of these oxides. It is shown that the first exchange type prevails in LaMnO_{3 + δ} occurring without participation of oxygen from the oxide surface. At the same time, in the case of LaCoO_{3 - δ}, an increase in the temperature results in a significant contribution of both the second and third exchange types with participation of one and two oxygen atoms of the oxide surface, accordingly. The rate determining exchange stage is the process of dissociative oxygen adsorption/desorption on the oxide surface.     

Crystal and molecular structure of benzoaza-12-crown-4 hydrochloride

Journal of Structural Chemistry - The X-ray crystallographic analysis of benzoaza-12-crown-4 hydrochloride crystals is performed for the first time: space group P1, a = 7.7497(4) Å, b =...