1,210 research outputs found
Properties of spatial arrangement of V-type defects in irradiated materials: 3D-modelling
We consider the dynamics of pattern formation in a system of point defects
under sustained irradiation within the framework of the rate theory. In our
study we generalize the standard approach taking into account a production of
defects by elastic fields and a stochastic production representing internal
multiplicative noise. Using 3D-modelling we have shown that with the damage
rate growth, a morphology of clusters composed of vacancies changes. The same
effect is observed with variation in the multiplicative noise intensity.
Stationary patterns are studied by means of correlation analysis.Comment: 12 pages, 7 figure
Ab-initio calculations for structural properties of Zr-Nb alloys
Ab-initio calculations for the structural properties of Zr-Nb alloys at
different values of the niobium concentration are done at zero temperature.
Different cases for Zr-Nb alloys with unit cells having BCC and HCP structures
are considered. Optimal values of the lattice constants are obtained. Critical
value for the niobium concentration corresponding to the structural
transformation HCP \rightarrow BCC at zero temperature is determined.
Electronic densities of states for two different structures with niobium
concentrations 12.5% and 25% having HCP and BCC structures, accordingly, are
studied.Comment: 8 pages, 4 figure
Universality and self-similar behaviour of non-equilibrium systems with non-Fickian diffusion
Analytical approaches describing non-Fickian diffusion in complex systems are
presented. The corresponding methods are applied to the study of statistical
properties of pyramidal islands formation with interacting adsorbate at
epitaxial growth. Using the generalized kinetic approach we consider
universality, scaling dynamics and fractal properties of pyramidal islands
growth. In the framework of generalized kinetics, we propose a theoretical
model to examine the numerically obtained data for averaged islands size, the
number of islands and the corresponding universal distribution over the island
size.Comment: 10 pages, 6 figure
Rocking Subdiffusive Ratchets: Origin, Optimization and Efficiency
We study origin, parameter optimization, and thermodynamic efficiency of
isothermal rocking ratchets based on fractional subdiffusion within a
generalized non-Markovian Langevin equation approach. A corresponding
multi-dimensional Markovian embedding dynamics is realized using a set of
auxiliary Brownian particles elastically coupled to the central Brownian
particle (see video on the journal web site). We show that anomalous
subdiffusive transport emerges due to an interplay of nonlinear response and
viscoelastic effects for fractional Brownian motion in periodic potentials with
broken space-inversion symmetry and driven by a time-periodic field. The
anomalous transport becomes optimal for a subthreshold driving when the driving
period matches a characteristic time scale of interwell transitions. It can
also be optimized by varying temperature, amplitude of periodic potential and
driving strength. The useful work done against a load shows a parabolic
dependence on the load strength. It grows sublinearly with time and the
corresponding thermodynamic efficiency decays algebraically in time because the
energy supplied by the driving field scales with time linearly. However, it
compares well with the efficiency of normal diffusion rocking ratchets on an
appreciably long time scale
Colored noise influence on the system evolution
We present a picture of phase transitions of the system with colored
multiplicative noise. Considering the noise amplitude as the power-law
dependence of the stochastic variable we show the way to phase
transitions disorder-order and order-disorder. The governed equations for the
order parameter and one-time correlator are obtained and investigated in
details. The long-time asymptotes in the disordered and ordered domains on the
phase portrait of the system are defined.Comment: 12 pages, 8 figures, LaTeX. Submitted to EPJ-
Morphology change of the silicon surface induced by Ar ion beam sputtering
Two-level modeling for nanoscale pattern formation on silicon target by
Ar ion sputtering is presented. Phase diagram illustrating possible
nanosize surface patterns is discussed. Scaling characteristics for the
structure wavelength dependence versus incoming ion energy are defined. Growth
and roughness exponents in different domains of the phase diagram are obtained.Comment: 11 pages, 5 figure
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