Russian Journal of Physical Chemistry A最新文献

Thermodynamic modeling of the Ga–Ge binary system was carried out with the help of the CALPHAD (CALculation of PHAse Diagram) method. The liquid and diamond (Ge) phases have been described with the sublattice formalism and the excess model with the Redlich–Kister equation. The solution phase (Ga) was treated as a pure element. The most experimental data, including phase diagrams and thermodynamic information, gathered from the literature were employed to optimize the thermodynamic parameters. The resultant calculated phase diagram and the system’s thermodynamic properties are in satisfactory accordance with the majority of the experimental data.

The kinetic model of the synthesis of methyl-tert-butyl ethers by intermolecular dehydration of tert-butanol with methanol using HY zeolite with a hierarchical structure as a catalyst (HY_mmm), as well as a catalyst system based on CuBr₂ deposited on HY_mmm, is considered. A kinetic model was constructed and a multistage scheme of chemical transformations was developed based on the experimental data. The kinetic model is based on the law of acting surfaces with allowance for adsorption and desorption processes on the catalyst surface. The inverse problem was solved in the form of a global optimization problem, which made it possible to determine the parameters of the kinetic model—the kinetic constants and activation energies.

The linear Scofield–Litster–Ho (LM) model is used to obtain a representation of the scaling hypothesis (SH) similar in structure to the SH representation. The new representation follows from the phenomenological theory of the Migdal critical point and allows the construction of an equation of state in physical variables, in accordance with the requirements of the scale theory. As in the Berestov critical point model, isochoric heat capacity reduced to absolute temperature (({{C}_{{v}}})/T) is used as a scale factor in the proposed critical point model. Based on Benedek’s hypothesis, scale functions of Helmholtz free energy in density–temperature variables not inferior to the corresponding LM scale functions can be calculated using the proposed SH model. In contrast to scale functions calculated on the basis of Migdal’s SH representations, free energy scale functions calculated within the proposed critical point model do not contain integrals of differential binomials. A unified fundamental equation of state in the context of the new SH concept is proposed and tested by describing the equilibrium properties of methane in the 90.6941–620 K range of temperatures at pressures up to 600 MPa.

Cyclic voltammetry is used to study the electrocatalytic activity in the formation of molecular hydrogen with condensed heterocyclic compounds 1,10-phenatroline and its derivatives 2,9-dimethyl-1,10-phenanthroline and 3,4,7,8-tetramethyl-1,10-phenanthroline using CF₃COOH. It is shown that the efficiency and mechanism of electrocatalysis depend strongly on the nature of the catalyst. Raising the number of methyl substituents in the heterocyclic framework improves the efficiency of the process (to more than the TOF value). Mechanisms of the processes are studied and key intermediates are identified via DFT within the context of the density functional theory (DFT) using the B3LYP hybrid functional in the 6-31++G basis.

Spinel type manganese oxide MnO₂⋅0.5H₂O (H_1.6Mn_1.6O₄) is considered one of the most promising precursors for lithium-ion sieves due to its high theoretical lithium adsorption capacity (72.3 mg/g), and is suitable for selectively extracting lithium from high magnesium lithium ratio brine. In this paper, the powdery lithium-ion sieve precursor Li_1.6Mn_1.6O₄ was prepared by two-step urea-assisted hydrothermal method combining with solid phase method, and the effects of urea/Mn ratios on the adsorption performance of lithium-ion sieves were explored. The results show that as the ratio of urea to Mn increases to 40, the particles tend to acquire a cubic morphology. Moreover, desorption of lithium during the acid leaching of the precursor becomes more favorable. The lithium-ion sieve pellets were prepared by the anti-solvent precipitation method. According to the calculated selectivity coefficient, the separation order by the pellets in the mixed solution is Li⁺ ( gg ) Na⁺ > Mg²⁺ > Ca²⁺, demonstrating the lithium-ion sieve has a high selectivity to lithium. The adsorption kinetics of lithium-ion sieve pellets in a solution containing lithium illustrates a chemical adsorption mode.

Detailed structural and computational studies of 2-((2-hydroxybenzylidene)hydrazineylidene)-2-phenylacetaldehyde oxime (1), using the DFT and molecular docking computations, are reported. The molecular structure of 1 is stabilized by a O–H⋅⋅⋅N hydrogen bond between the phenolic OH hydrogen atom and the nearest hydrazineylidene nitrogen atom, yielding a six-membered noncovalent ring, which, in turn, was found to be highly aromatic. Intermolecular O–H⋅⋅⋅N and C–H⋅⋅⋅N hydrogen bonds between molecules of 1 produce a 1D supramolecular polymeric chain of the zig-zag type. These chains are linked into a 2D supramolecular layer due to reciprocal π⋅⋅⋅π interactions formed between the phenylene and six-membered noncovalent rings. The reciprocal H⋅⋅⋅X (X = H, C, N, O) and C⋅⋅⋅Y (Y = C, N) contacts are the most prominent contributors to the crystal packing. The optimized molecule of 1 is a pronounced electrophile with the most nucleophilic sites found on the phenolic oxygen atom, oxime oxygen and nitrogen atoms, and one of the hydrazineylidene nitrogen atoms, while the oxime OH and some of the phenylene hydrogen atoms were revealed as the most eletrophilic sites. The discussed compound was found to be active against all the studied herein SARS-CoV-2 proteins. The best results were revealed against Papain-like protease (PLpro), nonstructural protein 14 (Nsp14_N7-MTase), and nonstructural protein 3 (Nsp3_range 207–379-MES), with the calculated ligand efficiency scores for complex PLpro–1 being within the recommended ranges for a Hit.

A new variational theory of the growth of particles of a new phase in supercooled multicomponent melts is developed. The crystallization of supercooled metal melts is characterized by various nonlinear effects on the surface of a growing crystal. A new variational means of nonequilibrium thermodynamics is developed to consider such effects, based on the principle of minimum entropy production. The approach allows the growth of an embryo of a new phase to be considered by allowing for the interrelated influence of thermal and diffusion processes, along with non-stationary effects associated with deviations from the local equilibrium on the surface of the growing embryo. The transfer of components across the phase boundary is described in the form of chemical reactions. An advantage of the theory is the possibility of obtaining a generalized theoretical description of nonlinear effects on the crystal’s surface. Expressions of crystal growth are given for different types of multicomponent metal systems to demonstrate the use of the approach.

The dependence of the melting temperature and enthalpy of fusion on the characteristic size and morphology of nanoobjects consisting of UO₂ and ThO₂ was studied by the thermodynamic method. The influence of the characteristic size and morphology on the enthalpy of fusion and melting temperature of UO₂ and ThO₂ nanoobjects becomes noticeable when their characteristic size is less than 20 nm. The melting point abruptly decreases when the characteristic size of nanoparticles, nanowires, and thin films of UO₂ and ThO₂ is less than 5, 4, and 3 nm, respectively. The size effect decreases in a sequence: spherical nanoparticles–nanowires–thin films in all cases. The size effect also decreases when individual UO₂ and ThO₂ nanoparticles are combined into nanostructured nanoobjects. The results of calculations obtained in the present study are in good agreement with the results of calculations obtained by molecular dynamics and experimental data available in the literature.

Crystallographic orientation is an important factor to affect the inhibition performance of metal materials, while the influence of crystallographic orientation of the pure aluminum metal on the electrochemical noise features during inhibition process is still unclear. In the present work, the inhibition behavior of 1,5-naphthalenediol on pure aluminum with different crystallographic orientations has been investigated using electrochemical techniques as well as some surface characterizations. Electrochemical impedance spectroscopy (EIS) results indicated that the pure aluminum specimen with (111) crystallographic orientation presented the highest corrosion resistance. The value of noise resistance calculated from electrochemical potential and current noise was positively correlated to the charge transfer resistance (R_ct) from EIS results. The parameter of corrosion energy (E_c) proposed from wavelet analysis of electrochemical noise data revealed an oppositely variation trend to R_ct with different crystallographic orientations. This observation was further confirmed by the X-ray photoelectron spectroscopy measurements. Lower E_c corresponded to stronger adsorption of inhibitors and E_c can be utilized as a potential criterion to estimate the corrosion rate and eventually ascertain the effect of crystallographic orientation on the inhibition performance.