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

Phase field modeling microstructural evolution of Fe-Cr-Al systems at thermal treatment

A phase field model to study dynamics of microstructure transformations and the evolution of defect structure during heat treatment of Fe-Cr-Al systems is developed. Statistical and kinetic properties of evolving microstructure and defect structure in alloys with different content of alloying elements and at different temperatures were studied. Point defects rearrangement during precipitation is discussed in details. Universality of statistical distributions over precipitate size is revealed for considered class of alloys

Stochastic effects at ripple formation processes in anisotropic systems with multiplicative noise

We study pattern formation processes in anisotropic system governed by the Kuramoto-Sivashinsky equation with multiplicative noise as a generalization of the Bradley-Harper model for ripple formation induced by ion bombardment. For both linear and nonlinear systems we study noise induced effects at ripple formation and discuss scaling behavior of the surface growth and roughness characteristics. It was found that the secondary parameters of the ion beam (beam profile and variations of an incidence angle) can crucially change the topology of patterns and the corresponding dynamics

Nano-sized Adsorbate Structure Formation in Anisotropic Multilayer System

Abstract In this article, we study dynamics of adsorbate island formation in a model plasma-condensate system numerically. We derive the generalized reaction-diffusion model for adsorptive multilayer system by taking into account anisotropy in transfer of adatoms between neighbor layers induced by electric field. It will be found that with an increase in the electric field strength, a structural transformation from nano-holes inside adsorbate matrix toward separated nano-sized adsorbate islands on a substrate is realized. Dynamics of adsorbate island sizes and corresponding distributions are analyzed in detail. This study provides an insight into details of self-organization of adatoms into nano-sized adsorbate islands in anisotropic multilayer plasma-condensate systems

Scaling properties of pyramidal islands formation process at epitaxial growth

We study scaling properties of the surface morphology at epitaxial growth in a generalized phase-field model by taking into account dynamics of the adsorbate temperature. We have found that growth processes are defined by a set of roughness and growth exponents. It is shown that the growth rate of the averaged mean area of islands can be controlled by deposition flux, interaction strength of adsorbate and time scale for the temperature relaxation. We have shown, that both number of islands and average island size behave in a power-law form over exposing time. We have discussed two different numerical approaches allowing one to determine the distribution function of islands over sizes. Obtained distributions are universal and do not change with variation in main system parameters

A study of void size growth in nonequilibrium stochastic systems of point defects

We study properties of voids growth dynamics in a stochastic system of point defects in solids under nonequilibrium conditions (sustained irradiation). It is shown that fluctuations of defect production rate (external noise) increase the critical void radius comparing to a deterministic system. An automodel regime of void size growth in a stochastic system is studied in detail. Considering a homogeneous system, it is found that external noise does not change the universality of the void size distribution function; the mean void size evolves according to classical nucleation theory. The noise increases the mean void size and spreads the void size distribution. Studying dynamics of spatially extended systems it was shown that vacancies remaining in a matrix phase are able to organize into vacancy enriched domains due to an instability caused by an elastic lattice deformation. It is shown that dynamics of voids growth is defined by void sinks strength with void size growth exponent varying from 1/3 up to 1/2

A study of pyramidal islands formation in epitaxy within the generalized phase-field model

We study epitaxial growth of pyramidal patterns in a framework of the phase-field model generalized by introduction of temperature field dynamics and an assumption of interacting adsorbate due to elastic effects. We have shown that in the system with different rates of the phase-field change oscillatory dynamics of surface pattern formation can be realized. Analytical results are verified by numerical simulations. We compare properties of surface structures within the framework of the standard phase-field model and proposed a generalized model of epitaxial growth using statistical approach. It is shown that in the generalized model pyramidal patterns can be sustained by thermodynamical force governing flux of interacting adsorbate