Formation of argon cluster with proton seeding

ABSTRACT

We employ force-field molecular dynamics simulations to investigate the kinetics of nucleation to new liquid or solid phases in a dense gas of particles, seeded with ions. We use precise atomic pair interactions, with physically correct long-range behaviour, between argon atoms and protons. Time dependence of molecular cluster formation is analysed at different proton concentration, temperature and argon gas density. The modified phase transitions with proton seeding of the argon gas are identified and analysed. The seeding of the gas enhances the formation of nano-size atomic clusters and their aggregation. The strong attraction between protons and bath gas atoms stabilises large nano-clusters and the critical temperature for evaporation. An analytical model is proposed to describe the stability of argon-proton droplets and is compared with the molecular dynamics simulations.     

Quantized Fermi Accelerator: A Soluble Model for Quantum Friction

The motion of a particle constrained to move inside a box with a movable wall is quantized. The semiclassical, adiabatic and exact solutions are worked out. The time-dependent density matrix is found in closed form. The motions of the heavy and the light parts of the system, described by appropriate reduced density matrices, are discussed. General comments about quantum friction are made.     

Hydroamination of pyrylium salts

The catalytic reductive amination of pyrylium salts proceeded stereoselectively to give piperidine bases with a cis-structure. The reaction involved the formation of a pyridine intermediate; the course of the reaction depended on the structure of both the substrate and the aminating agent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, 608–611, May, 1990.     

Influence of noise on the nature of synergetic systems

We have studied the stationary states of a homogeneous synergetic system in the presence of noise. In the framework of the subordination principle it is shown that, as a function of noise intensity in the system, transitions of both first and second order may be observed. The corresponding phase diagrams are presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 75–82, April, 1996.     

Reactions of 1,5-Diketones with Ammonia and Its Derivatives. (Review)

Published data and the authors' own experimental results on the reaction of aliphatic, semicyclic, and oxosemicyclic 1,5-diketones and alkylidene- and arylidene-2,2-dicyclanones with ammonia, ammonium acetate, and XNH₂ derivatives, where X = Alk, Ar, OH, NH₂, PhNH, ArCONH, and CHO, are reviewed. The characteristics and the relationships governing the transformations into azaheterocycles in relation to the nature of the reagents and the reaction conditions are discussed.     

Modeling phase decomposition and patterning in binary alloy systems subjected to neutron irradiation

We study processes of phase decomposition and patterning in a model of a binary alloy system subjected to sustained irradiation. We exploit the reaction rate theory and generalize the Darken approach of vacancy diffusion to describe generation, recombination, annihilation and spatial interaction of point defects. It is shown that an increase in the defect production rate phase, decomposition processes are replaced by disordering and patterning with vacancy clusters' formation. At elevated damage rates, both phase separation and patterning are accompanied by pattern selection processes. In the framework of numerical simulations, dynamics of phase decomposition and vacancy clusters formation is studied in detail. A change in the morphology of vacancy clusters during irradiation and their statistical properties are discussed.     

One-dimensional magnetophotonic crystals with magnetooptical double layers

One-dimensional magnetophotonic microcavity crystals with nongarnet dielectric mirrors are created and investigated. The defect layers in the magnetophotonic crystals are represented by two bismuth-substituted yttrium iron garnet Bi:YIG layers with various bismuth contents in order to achieve a high magnetooptical response of the crystals. The parameters of the magnetophotonic crystal layers are optimized by numerical solution of the Maxwell equations by the transfer matrix method to achieve high values of Faraday rotation angle Θ _F and magnetooptical Q factor. The calculated and experimental data agree well with each other. The maximum values of Θ _F =–20.6°, Q = 8.1° at a gain t = 16 are obtained for magnetophotonic crystals with m = 7 pairs of layers in Bragg mirrors, and the parameters obtained for crystals with m = 4 and t = 8.5 are Θ _F =–12.5° and Q = 14.3°. It is shown that, together with all-garnet and multimicrocavities magnetophotonic crystals, such structures have high magnetooptical characteristics.     

Modeling self-organization of nano-size vacancy clusters in stochastic systems subjected to irradiation

We study the self-organization of vacancy clusters in irradiated materials under reactor and accelerator conditions. Using a continuum stochastic model we take into account dynamics of point defects and their sinks with elastic interactions of vacancies. Dynamics of vacancy clusters formation is studied analytically and numerically. We have shown a difference in patterning dynamics at irradiation under reactor and accelerator conditions. The external noise influence related to fluctuation in a defect production rate is studied in detail. Applying our approach to pure nickel irradiated under different conditions we have shown that vacancy clusters having a linear size ～eq 6 nm can arrange in a statistical periodic structure with nano-meter range. We have found that the linear size of vacancy clusters at accelerator conditions decreases down to 20%, whereas a period of vacancy clusters reduces to 6.5%.