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41.
42.
The adsorption isotherms at 25, 45, and 65 degrees C of molybdenum solutions of concentration ranges between 10(-3) and 3x10(-2) M(Mo) (pH 4-5) on different alumina samples are investigated. The analysis is conducted using a modified Frumkin isotherm which takes a more realistic account of the lateral interaction between adsorbed species and considers that the adsorption takes place on the most basic OH groups on the surface of alumina. The results are discussed in view of the difference in solutions speciation, and the changes in the pH of the remaining supernatant solutions. The solution temperature, PZC of the used aluminas, the configuration of the basic OH groups on their surface, and the pore structure have been shown to intervene effectively. Copyright 2000 Academic Press. 相似文献
43.
Kireev V. V. Yakubovich O. V. Ivanov-Shits A. K. Mel'nikov O. K. Dem'yanets L. N. Skunman J. Chaban N. G. 《Russian Journal of Coordination Chemistry》2001,27(1):31-37
Crystals of Li2TiGeO5 were obtained by solution-melt crystallization, and those of Na2TiGeO5 were grown from a melt by pulling. The crystals are isostructural with the natisite mineral Na2TiSiO5. The crystal structure of Li2{TiOGeO4} was refined by X-ray diffraction analysis (a four-circle diffractometer, 2/ scan mode, MoK
radiation, max = 50°). The unit cell parameters are a = 6.614(4) Å and c = 4.435(4) Å; space group P4/nmm, Z = 2, calcd = 3.67 g/cm3, R = 0.031, s = 1.128, wR(F
2) = 0.071 (548 reflections with I 2I). The ionic conduction in both crystals was found to be anisotropic in the temperature range 250–600°C;. At 400°C;, the conductivity values are 10–4 to 10–5 S/cm along the a axis and 10–6 to 10–8 (for Na2TiGeO5) and 10–7 to 10–9 S/cm (for Li2TiGeO5) along the c axis. 相似文献
44.
The geometric parameters of the isomers HN2O+, HPNO+, and HP2O+ were calculated by the nonempirical SCF/3-21G* method and their relative energies were determined with consideration of the electronic correlation in the MP3/DEHD + PS approximation. According to the calculations, protonation of N2O, PNO, and P2O molecules should preferably take place at the oxygen atom. Isomers with a quasilinear NNO and PNO backbone are most advantageous in HN2O+ and HPNO+, and cyclic isomers are 60 and 30 kcal/mole less stable, respectively. On the contrary, the cyclic form is more stable for HPO
2
+
(by 10 kcal/mole). The bond at the attacked atom usually weakens (breaks) and the neighboring (opposite) bonds are strengthened in protonation. Protonation of P2O stabilizes the cyclic isomer by 15 kcal/mole more strongly than the "open" isomer, resulting in inversion of their position on the energy scale. In the case of N2O and PNO, the relative position of the cyclic and basic isomers virtually does not change, but the linear NPO isomer is destabliized. The stability of the cyclic isomers in comparison to the "open" isomers increases on substitution of N atoms by P atoms in both molecules of N2O, PNO, and P2O and in their ions HN2O+, HPNO+, and HP2O+. This tendency probably holds in subsequent transition to As and Sb atoms.Institute of New Chemical Problems, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 126–134, January, 1992. 相似文献
45.
A quasi-Newton method involving a diagonal guess orbital hessian with iterative updates has been proposed recently by Almlof
for the optimization of closed shell self-consistent field (SCF) wavefunctions. The technique is extended in the present work
to more general wavefunctions, ranging from open shell SCF through multiconfigurational SCF. A number of examples are presented
to show that convergence for closed and open shell SCF rivals conventional direct inversion in the iterative subspace (DIIS).
For multiconfigurational SCF wavefunctions, the method presented here requires more iterations than an exact second order
program, but since each iteration is substantially faster, leads to a more efficient overall program.
Received: 15 August 1996 / Accepted: 22 January 1997 相似文献
46.
Vibrational frequencies for fundamental, overtone, and combination excitations of sulfuric acid (H2SO4) and of sulfuric acid monohydrate cluster (H2SO4 x H2O) are computed directly from ab initio MP2/TZP potential surface points using the correlation-corrected vibrational self-consistent field (CC-VSCF) method, which includes anharmonic effects. The results are compared with experiment. The computed transitions show in nearly all cases good agreement with experimental data and consistent improvement over the harmonic approximation. The CC-VSCF improvements over the harmonic approximation are largest for the overtone and combination excitations and for the OH stretching fundamental. The agreement between the calculations and experiment also supports the validity of the MP2/TZP potential surfaces. Anharmonic coupling between different vibrational modes is found to significantly affect the vibrational frequencies. Analysis of the mean magnitude of the anharmonic coupling interactions between different pairs of normal modes is carried out. The results suggest possible mechanisms for the internal flow of vibrational energy in H2SO4 and H2SO4 x H2O. 相似文献
47.
I. S. Grudzinskaya Z. Ya. Kosakovskaya V. N. Reshetov A. A. Chaban 《Acoustical Physics》2001,47(5):548-551
The Young modulus of a thin layer consisting of densely packed carbon nanotubes oriented normally to a substrate is measured using a scanning probe atomic force microscope. It is found that the adhesion of the film and the silicon substrate is not very strong, and, at certain conditions, this may lead to an intense energy dissipation in an oscillatory system loaded by the film. 相似文献
48.
T. I. Chaban B. S. Zimenkovskii I. D. Komaritsa I. G. Chaban 《Russian Journal of Organic Chemistry》2012,48(2):268-272
By the reaction of acetylacetone and arylazoacetylacetones with 4-iminothiazolidin-2-one thiazolo[4,5-b]pyridines were obtained in good yields. Optimum reaction conditions were chosen and some properties of compounds obtained
were studied. 相似文献
49.
G. N. Kartsev N. M. Klimenko Zh. E. Grabovskaya G. M. Chaban 《Journal of Structural Chemistry》1989,29(6):931-933
M. V. Lomonosov Institute for Fine Chemical Technology, Moscow. Translated from Zhurnal Strukturnoi Khimii, Vol. 29, No. 6, pp. 126–128, November–December, 1988. 相似文献
50.
Matiichuk Yu. E. Horak Y. I. Chaban T. I. Horishny V. Ya. Tymoshuk O. S. Matiychuk V. S. 《Russian Journal of Organic Chemistry》2020,56(10):1720-1727
Russian Journal of Organic Chemistry - Reactions of 5-(1,3-benzothiazol-2-yl)furan-2-carbaldehyde with 2-acetylfuran, 2-acetylthiophene, and some compounds containing an active methylene group gave... 相似文献