排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
V. A. Popov S. I. Lopatin L. Sh. Tsemekhman L. A. Pavlinova S. P. Kormilitsyn V. V. Barsegyan 《Russian Journal of Applied Chemistry》2003,76(10):1564-1567
Evaporation of chromium ore and concentrates was studied using high-temperature differential mass-spectrometry. The data obtained, concerning the component vapor pressures in evaporation of complex oxide systems in the range 1700-2100 K, can be used to calculate the evaporation loss in melting and to assess the possibility of utilization of the sublimates formed. 相似文献
2.
Dmitri S. Kilin Kiril Tsemekhman Oleg V. Prezhdo Eduard I. Zenkevich Christian von Borczyskowski 《Journal of photochemistry and photobiology. A, Chemistry》2007,190(2-3):342-351
The observed resonance energy transfer in nanoassemblies of CdSe/ZnS quantum dots and pyridyl-substituted free-base porphyrin molecules [Zenkevich et al., J. Phys. Chem. B 109 (2005) 8679] is studied computationally by ab initio electronic structure and quantum dynamics approaches. The system harvests light in a broad energy range and can transfer the excitation from the dot through the porphyrin to oxygen, generating singlet oxygen for medical applications. The geometric structure, electronic energies, and transition dipole moments are derived by density functional theory and are utilized for calculating the Förster coupling between the excitons residing on the quantum dot and the porphyrin. The direction and rate of the irreversible exciton transfer is determined by the initial photoexcitation of the dot, the dot–porphyrin coupling and the interaction to the electronic subsystem with the vibrational environment. The simulated electronic structure and dynamics are in good agreement with the experimental data and provide real-time atomistic details of the energy transfer mechanism. 相似文献
3.
Eric J. Bylaska Kiril Tsemekhman Scott B. Baden John H. Weare Hannes Jonsson 《Journal of computational chemistry》2011,32(1):54-69
Semi‐local functionals commonly used in density functional theory (DFT) studies of solids usually fail to reproduce localized states such as trapped holes, polarons, excitons, and solitons. This failure is ascribed to self‐interaction which creates a Coulomb barrier to localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid‐DFT, e.g., B3LYP and PBE0) have shown to promise in rectifying this type of failure, as well as producing more accurate band gaps and reaction barriers. The evaluation of exact exchange is challenging for large, solid state systems with periodic boundary conditions, especially when plane‐wave basis sets are used. We have developed parallel algorithms for implementing exact exchange into pseudopotential plane‐wave DFT program and we have implemented them in the NWChem program package. The technique developed can readily be employed in Γ‐point plane‐wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car‐Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
4.
Conversion of organosulfur components (COS and CS2) in catalytic processing of a real reduced sulfurous gas was experimentally studied. 相似文献
5.
The energy of alpha helix formation is well known to be highly cooperative, but the origin and relative importance of the contributions to helical cooperativity have been unclear. Here we separate the energy of helix formation into short range and long range components by using two series of helical dimers of variable length. In one dimer series two monomeric helices interact by forming hydrogen bonds, while in the other they are coupled only through long range, primarily electrostatic interactions. Using Density Functional Theory, we find that approximately half of the cooperativity of helix formation is due to electrostatic interactions between residues, while the other half is due to nonadditive many-body effects brought about by redistribution of electron density with helix length. 相似文献
6.
Fedorova N. A. Tsymbulov L. B. Tsemekhman L. Sh. 《Russian Journal of Applied Chemistry》2003,76(4):526-530
The equilibrium between a copper-nickel alloy and an oxide melt in the Cu2O-NiO-SiO2 system was studied experimentally. The distribution coefficients of nickel were determined as a function of the content of silicon dioxide, and the ratio of activity coefficients of nickel and copper oxides at 1300°C was found. 相似文献
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Fedorova N. A. Tsymbulov L. B. Tsemekhman L. Sh. 《Russian Journal of Applied Chemistry》2002,75(4):521-525
Equilibria between a copper-nickel alloy and oxide melt of the binary system Cu2O-NiO were studied and the activity coefficients of copper and nickel oxides at 1573 K in the homogeneity region of the oxide melt (up to 11.6 mol % NiO) were determined. Similar values were also found by calculation from the phase diagram of Cu2O-NiO. 相似文献
9.
The solubility of carbon in iron-nickel sulfide melts at 1673 K was studied in the entire range of compositions of the Fe-FeS-Ni3S2-Ni tetragon. The boundaries of the stratification area were determined in this system upon its being saturated with carbon. Lines of carbon isosolubility are plotted in the tetragon field outside the stratification area. 相似文献
10.
Fedorova N. A. Tsymbulov L. B. Tsemekhman L. Sh. 《Russian Journal of Applied Chemistry》2003,76(2):175-179
An experimental study of the equilibrium between the bottom phase (sulfide melt or copper) and slag in neutral and oxidizing atmospheres yielded dependences of the content of dissolved copper, nickel, and cobalt in the slag on that of sulfur in the sulfide melt and also the dependence of the content of dissolved copper and nickel on that of nickel in the metallic melt. The distribution coefficients of the metals between copper and slag were determined and compared with the results of other investigations. 相似文献