First-Principles Calculations of Phonons and Thermodynamic Properties of Zr(Hf)S2-Based Nanotubes

Comparative hybrid density functional calculations on the structure, stability, and phonon frequencies of monolayers and single-walled nanotubes are performed for Zr(Hf)S₂ disulfides. The first-principles calculations of HfS₂-based nanotubes are made for the first time. The symmetry analysis of infrared and Raman active vibrational modes in ZrS₂ and HfS₂ nanotubes is made using the induced representations of the isogonal point groups of line groups. It is shown that the number of infrared and Raman active modes is constant for NTs with the same chirality type. The correlation of the phonon modes of the nanotubes of relatively large diameters with those of monolayer is analyzed. The thermodynamic functions of monolayers and nanotubes with various chirality and diameters are calculated on the basis of the obtained phonon frequencies. It is established that the phonon contribution to the nanotube strain energy is small, but may be important for an accurate estimate of the stability of the nanotubes of small diameters. The calculated results show that the thermal contributions to Helmholtz free energy are positive; thereby they slightly reduce the stability of ZrS₂ and HfS₂ nanotubes at elevated temperatures. © 2019 Wiley Periodicals, Inc.     

Synthesis and properties of 5-alkynyl-1,2,3-triazoles

1,3-Dipolar addition was investigated of 2-azidoethanol to diyne glycols containing primary or tertiary hydroxyethyl groups at the system of triple bonds. This reaction provided exclusively a monoadduct as a single regioisomer, namely, 5-alkynyl-1,2,3-triazole.     

A Spectrophotometric Study of Solid-Phase Topochemical Polymerization of Diyne Arylcarbamates and Logistic Representation of Results

Application of a logistic regression to interpretation of results is illustrated by spectrophotometric data on solid-state polymerization of symmetric and asymmetric diyne carbamates.     

Formation of a stable polymer blue phase under UV irradiation of Langmuir-Schaefer films of diin N-arylcarbamate derivative

Polymerization under UV irradiation is studied in monolayer Langmuir-Schaefer films of diin N-arylcarbamate derivative. The formation of a stable polymer blue phase of diacetylene derivative stable against excess UV light and heating to a temperature of 120 °C was detected. The formation of the structurally ordered Langmuir monolayer of monomers is studied using Brewster angle microscopy.     

复合模型和∑的四体衰变

本文计算了∑的四体衰变在∑的复合模型和通常的理论中的几率W^奇和W^偶,得到W^奇比W^偶约大50倍。W^奇为的β衰变几率的2—3％。     

Über den isomerisierungsmechanismus phenylsubstituierter cyclopropene

The thermal and thermocatalytic isomerisations of methyl 2,3,3-triphenylcyclopropene-1-carboxylate to methyl 2,3-diphenylindene-1-carboxylate have been studied. The rate constants of cyclopropene ring opening were determined and parameters of activation were calculated for the thermal process. The formation of cyclopropene and indene derivatives under the photochemical decomposition of methyl 3,3,5-triphenylpyrazolenine-4-carboxylate is discussed.     

Reaction of diphenyldiazomethane with phenylpropiolaldehyde

Two isomeric pyrazolenines — 4-formyl-3,3,5-triphenylpyrazolenine and 5-formyl-3,3,4-triphenylpyrazolenine — are formed as a result of the reaction of diphenyl-diazomethane with phenylpropiolaldehyde. The experimental data and the calculated values relative to the orientation of the addition of diazoalkanes and unsymmetrically substituted alkynes are discussed. The thermal transformations of the isomeric pyrazolenines were studied, and it is shown that the thermolysis of 5-formyl-3,3,4-pyrazolenine can serve as a method for the synthesis of 1-formyl-2,3,3-triphenylcyclopropene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1091–1096, August, 1978.     

Fragmentation of some 4<Emphasis Type="Italic">H</Emphasis>-pyran-4-one and pyridin-4-one derivatives under electron impact

Fragmentation of 13 compounds of the 4H-pyran-4-one and pyridin-4-one series under electron impact involves formation of rearrangement ions stabilized by multiple bonds and oxygen atoms (mostly [RC≡O]⁺ and RCH=OR′]⁺), as well of neutral molecules with low enthalpies of formation (CO, H₂O, CH₂O, CO₂, CH₂=C=O, C₃O₂, and RCOOH; R = H, Me, HC≡C, HOC≡C).