Russian Journal of Physical Chemistry A最新文献

Atomic force microscopy, scanning electron microscopy, X-ray diffraction phase analysis, voltammetry, and chronopotentiometry are used to study the physicochemical properties of lead coating on steel substrates obtained galvanically. The effect the oxidized surface layer and through pores in the lead coating have on the coating’s function as an anode of chemical power sources is analyzed. It is shown that at positive temperatures, the anodic oxidation of the steel substrate can contribute to the functioning of the anode during a discharge. The high discharge characteristics of lead-coated anodes with no barrier layers on steel substrates at temperatures of −50 to +50°С are confirmed by tests of pilot batches of Pb/HClO₄/PbO₂ reserve power sources. The potential of using tin–lead alloy POS 63 on copper substrates to manufacture anodes for chemical power sources is demonstrated.

Embedded atom model (EAM) potentials are proposed for liquid silicon and germanium. The potentials are calculated from diffraction data using Shommers’ algorithm and presented in the form of tables and piecewise continuous polynomials. Each pair term contributed to the potential takes the form of a hard-sphere model with a downward step. Properties of liquid Si and Ge (density, energy, bulk modulus, and coefficients of self-diffusion) are calculated at temperatures up to 2000 K and agree well with experimental data. It is found that bond directionality virtually disappears after melting at typical densities of liquid Si and Ge. It is suggested that bond directionality might reemerge upon heating and reducing the melt densities by 200–300%.

In this paper, a new simple, and the easy analytical formula is proposed to calculate the second virial coefficient with Yukawa potential. As it is known, the suggested analytical formula can be used to investigate some thermodynamic properties and predictors for protein crystallization and intermolecular interaction potential of fluids. The formula is tested for gas-liquid critical points and Hard-core Yukawa potential with different interaction ranges. The calculation results have been compared with different methods in literature data and the results agree with the literature data. Note that the second virial coefficient can provide significant results in the evaluated protein crystallization and investigate the gas-liquid separation with critical temperature.

Thermodynamic properties of (CaO)_0.501(Al₂O₃)_0.098(SiO₂)_0.401 (Ca40.10) glass are studied using two techniques: low-temperature vacuum adiabatic calorimetry and high-temperature drop solution calorimetry. The enthalpy of formation from oxides (−17.6 ± 2.6 kJ/mol) is determined for the first time. Heat capacity is shown to grow monotonically with temperature in the interval of 8 to 357 K. No phase transitions are revealed in this region of temperatures. Results from measuring heat capacity are approximated using the semi-empirical Planck–Einstein model. The possibility of using incremental scheme to estimate the heat capacity of ternary glasses formed by calcium, aluminium, and silicon oxides is confirmed.

Gibbs energies of the transfer of cryptand[2.2.2] from water to a water–ethanol solvent of variable composition are determined from the interphase distribution of the substance between immiscible phases at a temperature of 298 K composition. It is established that the solvation of cryptand[2.2.2] weakens upon an increase in the concentration of alcohol in the solution. Literature data are used to calculate Gibbs energies of the transfer of protonated cryptand[2.2.2] and complexes of it with nickel(II) and copper(II) ions from water to water–ethanol mixtures.

An experiment is performed on introducing methane with a syringe at different helium flow rates on a chromatographic column free of adsorbent. It is found that the input signals generated in this case are satisfactorily described by an elution curve equation that is a correct solution to the direct problem of linear adsorption dynamics. A separate example shows that the input signals at the same flow rate coincide with one another quite well. The centers of gravity to the left and right of the input signal’s maximum are calculated, considerably expanding its content of information.

Results are presented from studying the permeability of Nafion-type perfluorinated sulfonic cation-exchange membranes used in membrane contact devices (MCDs) for chemical isotopic exchange between water and hydrogen. It is shown that the permeability of a perfluorinated sulfonic cation-exchange membrane grows after modifying it with Fe³⁺ ions and subsequent regeneration with a nitric acid solution. The best effect is observed for Nafion 212 membrane (50.8 µm), since its permeability is approximately tripled in the 298–343 K range of temperatures. It is shown that the state of a membrane has no effect on the observed energy of activation. Energy E_a = 14 ± 4 kJ/mol indicates that isotopic exchange is controlled by diffusion processes.

Protonated methane, ({text{CH}}_{5}^{ + }), has unusual vibrational and rotational behavior because its three nonequivalent equilibrium structures have nearly identical energies and its five protons scramble freely. The highly flexible ({text{CH}}_{5}^{ + }), molecular ion has been shown by ab initio calculations to have 120 symmetrically equivalent minima of Cs symmetry in its ground electronic state. Complete proton rearrangement, making all minima accessible to each other, is possible as a result of two large-amplitude internal motions: an internal rotation about the C₃ axis with an ab initio barrier of 30 cm^–1 and an internal flip motion with an ab initio barrier of 300 cm^–1 that exchanges protons between the H₂ and ({text{CH}}_{3}^{ + }) groups. We calculate the structure of the J = 2 ( leftarrow )1 and 1 ( leftarrow ) 0 rotational transitions of ({text{CH}}_{5}^{ + }), ({text{CD}}_{5}^{ + }) and also other variants containing ({text{C}}{{{text{H}}}_{x}}{text{D}}_{{(5 - x)}}^{ + }). Although many theoretical papers have been published on the quantum mechanics of these systems, a better understanding requires spectral and conformational analysis. Post Hartree-Fock, Møller-Plesset and DFT calculation with the correlation consistent polarized valence double and triple zeta basis sets have done for the zero-point energies of ({text{C}}{{{text{H}}}_{x}}{text{D}}_{{(5 - x)}}^{ + }). The present results indicates the mode 8, 12, and 10 agree with qualitative of ({text{CH}}_{5}^{ + }), which is highly fluxional and has a complex spectrum while the C–X bonds which are broken and reformed all the time. The spectrum of mode 12 is highly complex with huge red-and some blue shifts. In particular, they can be attributed to the rapid coupling of the original CH-stretching normal mode to motions more closely related to isomerization, i.e., bending or rocking. There has thus been a long debate whether ({text{CH}}_{5}^{ + }) has a structure at all or not and is it real rotational motions or artificial. In addition, we include the contribution to the torsional barrier from the zero point energies of the other (high-frequency) vibrations, the effect of centrifugal distortion, and the effect of second-order rotation-vibration interactions.

Molecular dynamics is used to calculate the vapor–liquid equilibrium and liquid–vapor surface tension for a methane–ethane system. Good agreement of the parachor value for ethane between the molecular model and experimental data is shown for the 203–253 K range of temperatures and pressures up to 60 atm. The dependence of the surface tension of the mixture on pressure in the range of 4–40 atm at a temperature of 213 K shows a drop in both the surface tension and the difference in densities between the liquid and vapor as the pressure rises and approaches the critical locus. Approximating the density profiles obtained for the same conditions, it is concluded that the width of the interphase boundary also grows. The amount of methane adsorbed on the surface of the liquid film is calculated. The dependence of the molar adsorption of methane on the difference between the densities of the components in the liquid and gas phases is obtained, along with its analytical expression in the context of the Gibbs theory. Features of the approach that is used include no need for approximations of the ideal gas or the ideal solution, and the use of only experimentally obtained data as input. The resulting values of methane adsorption are in good agreement with the derived analytical dependence.