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191.
Two phase transitions are revealed for the first time in Ag3Sc2(PO4)3 single crystals in the vicinity of the temperatures 303 and 165–180 K. It is established that the phase transition at 303
K corresponds to the well-known phase transition to the superionic state in Na3Sc2(PO4)3 single crystals in the temperature range 423–433 K, whereas the phase transition observed in the temperature range 170–180
K corresponds to the phase transition from the rhombohedral to monoclinic phase at about 320 K in the monoclinic Na3Sc2(PO4)3 single crystals. It is also established that rhombohedral Na3Sc2(PO4)3 single crystals undergo the second phase transition.
__________
Translated from Kristallografiya, Vol. 50, No. 1, 2005, pp. 122–126.
Original Russian Text Copyright ? 2005 by Shilov, Atovmyan, Kovalenko. 相似文献
192.
Furer VL Vandukova II Tatarinova EA Muzafarov AM Kovalenko VI 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(3):692-699
The FTIR spectra of G(3), G(4), and G(9) generations of polybutylcarbosilane dendrimers have been recorded and analyzed. The structural optimization and normal mode analysis were performed for G(1) generation on the basis of density functional theory (DFT). This calculation gave vibrational frequencies and infrared intensities for the t,t- and g,-g-conformers of the butyl terminal groups, attached to the same silicon atom. The g,-g-conformer is 5.83 kcal/mol less stable compared to t,t-conformer. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the studied dendrimers. The dependence of band full width at half height in the IR spectra on generation number is established. The IR spectra of carbosilane dendrimers at higher temperatures at the ambient air and isolated from atmosphere air were studied. At temperature 180 degrees C all studied carbosilane dendrimers are stable when contact with atmosphere is absent, in the air they oxidize and thus CO and SiO groups appear. 相似文献
193.
Furer VL Vandyukova II Vandyukov AE Majoral JP Caminade AM Kovalenko VI 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):1110-1118
FTIR and FT-Raman spectra of four generations of phosphorus-containing dendrons with terminal aldehyde or PCl groups have been recorded and analyzed. Their spectral patterns are determined by the ratio T/R (T, the number of terminal groups; R, the number of repeated units). Bands assigned to the core, repeated units and terminal groups were separated by the difference spectroscopy method. The optimized geometry, frequencies and intensity of IR bands of G(1v) generation dendron with terminal aldehyde groups were obtained by the density functional theory (DFT). It was found that the internal skeleton of molecules exists in a single stable conformation with planar O-C(6)H(4)-CHN-N(CH(3))-P(S) fragments, but terminal groups may adopt the t,g,g- and t,-g,g-rotational isomers. The t,-g,g-conformer is 0.74 kcal/mol less stable compared to the t,g,g-conformer. The bond length and bond angles obtained by DFT show the best agreement with experimental data. Relying on DFT calculations a complete assignment of vibrations is proposed for different parts of the studied dendrons. The calculated frequencies and intensity of IR bands of the t,g,g- and t,-g,g-conformers of G(1v) are found to be in reasonable agreement with the experimental results. The most reactive site in dendron is the core function and vinyl group is preferred for nucleophilic attack. In dendrimer the most reactive are the terminal groups. 相似文献
194.
Druzhinin SI Dubbaka SR Knochel P Kovalenko SA Mayer P Senyushkina T Zachariasse KA 《The journal of physical chemistry. A》2008,112(13):2749-2761
The newly synthesized aminobenzonitriles with two bulky amino substituents 4-(di-tert-butylamino)benzonitrile (DTABN) and 3-(di-tert-butylamino)benzonitrile (mDTABN) have strongly twisted amino groups in the ground state. From X-ray crystal analysis it is found that the amino twist angle theta of mDTABN equals 86.5 degrees , whereas a twist angle of around 75 degrees is deduced for DTABN from the extinction coefficient of its lowest-energy absorption band in n-hexane. Because of the electronic decoupling between the amino and benzonitrile groups caused by these large twist angles, the absorption of DTABN and mDTABN is relatively weak below 40000 cm-1, with extinction coefficients around 25 times smaller than those of the planar 4-(dimethylamino)benzonitrile (DMABN). DTABN as well as mDTABN undergo efficient intramolecular charge transfer (ICT) in the singlet excited state, in nonpolar (n-hexane) as well as in polar (acetonitrile) solvents. Their fluorescence spectra consist of an ICT emission band, without evidence for locally excited (LE) fluorescence. The occurrence of efficient ICT with mDTABN is different from the findings with all other N,N-dialkylaminobenzonitriles in the literature, for which ICT only appears with the para-derivative. From solvatochromic measurements, an ICT dipole moment of 17 D is determined for DTABN as well as for mDTABN, similar to that of DMABN. The picosecond fluorescence decays of DTABN (time resolution 3 ps) are effectively single exponential. Their decay time is equal to the ICT lifetime tau'0(ICT), which increases with solvent polarity from 0.86 ns in n-hexane to 3.48 ns in MeCN at 25 degrees C. The femtosecond excited-state absorption (ESA) spectra of DTABN in n-hexane and MeCN at 22 degrees C show a decay of the LE and a corresponding rise of the ICT absorption. The ICT reaction time is 70 fs in n-hexane and 60 fs in MeCN. DTABN and mDTABN may have a strongly twisted ICT state, similar to that of 6-cyanobenzoquinuclidine but different from that of DMABN. 相似文献
195.
Interaction of 3‐(2‐Aminophenyl)‐6‐R1‐1,2,4‐triazin‐5‐ones with Acylating Reagents: An Efficient Method for Preparation of 6‐Substituted 3‐R1‐2H‐[1,2,4]triazino[2,3‐c]quinazolin‐2‐ones 下载免费PDF全文
Alexey Yu. Voskoboynik Dmitriy Yu. Scorina Tetiana Yu. Sergeieva Sergiy I. Kovalenko Sergiy I. Okovytyy Irina V. Omelchenko Oleg V. Shishkin 《Journal of heterocyclic chemistry》2016,53(3):776-783
The series of 6‐substituted 3‐R1‐2H‐[1,2,4]triazino[2,3‐c]quinazolin‐2‐one was prepared via condensation of 3‐(2‐aminophenyl)‐6‐R1‐1,2,4‐triazin‐5‐ones with acylating reagents. Particularities of 1H NMR spectra have been also discussed based on the comparison of experimental and theoretical results for 3‐methyl‐6‐phenyl‐2H‐[1,2,4]triazino[2,3‐c]quinazolin‐2‐one and its 4,3‐isomer. 相似文献
196.
S. A. Mareev D. Yu. Butyl’skii A. V. Kovalenko N. D. Pis’menskaya L. Dammak C. Larchet V. V. Nikonenko 《Russian Journal of Electrochemistry》2016,52(10):996-1000
The applications of the Sand equation in potentiometry of electrode and membrane systems for precise measurements of the transition time (τ) have been determined. An approach was suggested for choosing the diffusion coefficient of electrolyte (D) in the case when the concentration changes from its value in the agitated solution (where D = Db) to the nearly zero value at the surface (D = D0 corresponds to an infinitely dilute solution), Db and D0 being substantially different. The Nernst–Planck–Poisson nonstationary equations were numerically solved in a one-dimensional system including an ion-exchange membrane and two adjacent diffusion layers (for the electrode–solution system, the result is a particular case). An effective value Def was found, whose substitution in the Sand equation gave τ identical to that obtained by numerical solution. The neglect of the concentration dependence D(с) can lead to a nonadequate determination of the ion transport numbers in the membrane. 相似文献
197.
V. G. Peshekhonov A. I. Mashoshin A. V. Shafranyuk V. Yu. Korchak V. V. Kovalenko A. G. Luchinin A. I. Malekhanov E. A. Mareev I. P. Smirnov A. I. Khil’ko V. N. Kravchenko I. M. Prikhod’ko 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(10):1229-1236
A concept for designing network systems for underwater observations based on the joint development of hydroacoustic radiating and receiving elements integrated with different channels of communication is discussed. The main requirements for such systems, principles, and algorithms of their operation under nonstationary conditions of actual marine waters are formulated. The results from several numerical and field experiments demonstrating the performance of certain elements of such systems in typical shallow water basins are presented. 相似文献
198.
V. L. Ivanov R. R. Akhmetshin A. N. Amirkhanov A. V. Anisenkov V. M. Aulchenko V. S. Banzarov N. S. Bashtovoy D. E. Berkaev A. V. Bragin S. I. Eidelman D. A. Epifanov L. B. Epshteyn A. L. Erofeev G. V. Fedotovich S. E. Gayazov A. A. Grebenuk D. N. Grigoriev E. M. Gromov F. V. Ignatov S. V. Karpov V. F. Kazanin B. I. Khazin I. A. Koop O. A. Kovalenko A. N. Kozyrev E. A. Kozyrev P. P. Krokovny A. E. Kuzmenko A. S. Kuzmin I. B. Logashenko P. A. Lukin K. Yu. Mikhailov V. S. Okhapkin Yu. N. Pestov E. A. Perevedentsev A. S. Popov G. P. Razuvaev Yu. A. Rogovsky A. L. Romanov A. A. Ruban N. M. Ryskulov A. E. Ryzhenenkov V. E. Shebalin D. N. Shemyakin B. A. Shwartz D. B. Shwartz A. L. Sibidanov Yu. M. Shatunov P. Yu. Shatunov E. P. Solodov V. M. Titov A. A. Talyshev A. I. Vorobiov Yu. V. Yudin 《Physics of Atomic Nuclei》2016,79(2):251-259
We report preliminary results on the cross section of the process e+e? → φ(1020)η measured at 30 center-of-mass energy points in the range from 1.59 up to 2.0 GeV. Data analysis is based on the integrated luminosity of 22 pb?1 collected with the CMD-3 detector in 2011–2012. The obtained cross section agrees with the BaBar measurement and has better statistical accuracy. 相似文献
199.
S. E. Maksimov N. Kh. Dzhemilev S. F. Kovalenko V. I. Tugushev O. F. Tukfatullin Sh. T. Khozhiev 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(2):101-104
Results from a comparative SIMS study of the fragmentation of metal clusters sputtered with atomic Xe+ and molecular SF5+ ions are presented. It is shown that the average decay rate constants and, hence, the excitation energies of clusters of the same stoichiometry do not depend on the type of bombarding ions. 相似文献
200.
Sokolov MN Gushchin AL Kovalenko KA Peresypkina EV Virovets AV Sanchiz J Fedin VP 《Inorganic chemistry》2007,46(6):2115-2123
The reaction of aqueous [W3S7(C2O4)3](2-) with Ln(3+) and Th(4+) in a 1:1 molar ratio leads to oxalate-bridged heteropolynuclear molecular complexes and coordination polymers. La(3+) and Ce(3+) give a layered structure with big (about 1.8 nm) honeycomb pores which are filled with water molecules and lanthanide ions, in {[Ln(H2O)6]3[W3S7(C2O4)3]4}Br x xH2O (Ia and Ib). The smaller Pr(3+), Nd(3+), Sm(3+), Eu(3+), and Gd(3+) ions give discrete nanomolecules [(W3S7(C2O4)3Ln(H2O)5)2(mu-C2O4)] (with a separation of about 3.2 nm between the most distant parts of the molecule), which are further united into zigzag chains by specific S2...Br- contacts to achieve the overall stoichiometry K[(W3S7(C2O4)3Ln(H2O)5)2(mu-C2O4)]Br.xH2O (IIa-IId). Th(4+) gives K2[(W3S7(C2O4)3)4Th2(OH)2(H2O)10] x 14.33H2O (III) with a nanosized discrete anion (with a separation of about 2.7 nm between the most distant parts of the molecule), in which two thorium atoms are bound via two hydroxide groups into the Th2(OH)2(6+) unit, and each Th is further coordinated by five water molecules and two monodentate [W3S7(C2O4)](2-) cluster ligands. All compounds were characterized by X-ray structure analysis and IR spectroscopy. Magnetic susceptibility measurements in the temperature range of 2-300 K show weak antiferromagnetic interactions between two lanthanides atoms for compounds IIa, IIb, and IId. The thermal decomposition of Ia, Ib, and IIb was studied by thermogravimetry. 相似文献