Materials physics and mechanics

RAR RUS 1-12 Ioffe Institute Bessolov

St.Petersburg, Russia

P-4505-2016 7006034020 0000-0002-2973-8645 Institute of Problems of Mechanical Engineering RAS Kukushkin S.A. sergey,a.kukushkin@gmail.com

St.Petersburg, Russia

Institute of Problems of Mechanical Engineering RAS Osipov A.V.

St.Petersburg, Russia

Foundation for the Advancement of Science and Education Luk'yanov

St.Petersburg, Russia

Heteroepitaxy of Gallium Nitride Layers: the Role of Initial Stages in Film Formation The process of nucleation and subsequent evolution of GaN on the substrate surface covered with a buffer layer was investigated theoretically. The rates of nuclei flows and the size distribution functions for the islands formed at substrate temperatures T > 480 °C were calculated for substrates covered with AlN buffer layers. All the major mechanisms of island growth were considered. It has been shown that at a temperature of T = 480 °C islands of liquid Ga are first formed. Next, chemical reactions between gallium and nitrogen with formation of GaN take place on the substrate surface. At 750 °C > T ≥ °C, only GaN is nucleated. The Ostwald ripening process in an ensemble of GaN islands was studied and a phase diagram of such an ensemble constructed. Gallium Nitride Heteroepitaxy Modeling https://mpm.spbstu.ru/article/2003.8.1/ MPM_6_1_P01.pdf

RAR RUS 13-20 Universidade de São Paulo B.J. Mokross

São Carlos, SP, Brazil

Nucleation Theory and Small System Thermodynamics The exact treatment of first-order phase transition is an important topic in thermodynamics. This topic exists as an exact branch of thermodynamics, only by virtue of the occurrence of sharp discontinuities in properties of macroscopic systems. In small systems, instead of such discontinities, there are more or less gradual changes which approach discontinuities more closely as the system becomes larger. Metastable macroscopic systems below a critical temperature show nucleation phenomena and depending on the saturation degree the number of constitutive elements that form the evolving nuclei may vary from a couple of tens to hundreds of thousands. In Classical Nucleation Theory specific corrections done on Gibbs surface tension term take care of small size effects and theoretical predictions are in fair agreement with early experimental data. However results obtained by experimental techniques developed in the last decade revealed systematic deviations from the classical theory. Nuclei that evolve into the new phase may contain only a few of tens of molecules and continuum thermodynamics does not apply to such situations. Statistical mechanical methods rely on complex interaction potentials and the generality of thermodynamic predictions is lost. However clever modifications introduced in continuum thermodynamics extend its applicability to small systems even in cases where the thermodynamic limit is not valid anymore. In all those treatments the grand canonical potential is of central importance and the driving force for nucleation is the entropy, whatever the nucleation process maybe. Nucleation Theory First-order phase transition Thermodynamics https://mpm.spbstu.ru/article/2003.8.2/ MPM_6_1_P02.pdf

RAR RUS 21-33 Universität Rostock Schmelzer

Rostock, Germany

Kinetic and Thermodynamic Theories of Nucleation An overview on selected thermodynamic and kinetic aspects of the theoretical description of first-order phase transitions, and, in particular, of the theory of nucleation is given. Hereby both basic concepts as well as modern developments in this field are discussed. Details can be traced in the literature cited and in the given there further references. The analysis is directed here mainly to phase formation processes in non-crystalline materials. However, the majority of the methods employed and results discussed are, possibly with quantitative modifications, applicable to phase formation processes in any other fields of interest as well. Nucleation Kinetic Theories Thermodynamic Theories https://mpm.spbstu.ru/article/2003.8.3/ MPM_6_1_P03.pdf

RAR RUS 34-42 IBM Research, Zurich Research Laboratory Müller

Rüschlikon, Switzerland

Finite Size Effects on Surface Excess Quantities and Application to Crystal Growth and Surface Melting of Epitaxial Layers From a macroscopic viewpoint phase transitions as surface melting or growth mode can be described in terms of Gibbs excess quantity duly amended by size effect. The aim of this study is to consider such amended quantities to describe surface melting and Stranski-Krastanov transition of epitaxial layers. The size effect so introduced allows to predict the equilibrium thickness of the wetting layer of Stranski-Krastanov growth mode and to describe and classify two different melting cases: the incomplete premelting relayed by a first order transition and the continuous premelting relayed by continuous overheating. Epitaxial Layers Crystal Growth Surface Melting Size Effects https://mpm.spbstu.ru/article/2003.8.4/ MPM_6_1_P04.pdf

RAR RUS 43-48 Institute of Physics, Academy of Sciences of the Czech Republic Demo

Praha, Czech Republic

Institute of Physics, Academy of Sciences of the Czech Republic Sveshnikov

Praha, Czech Republic

Institute of Physics, Academy of Sciences of the Czech Republic Nitsch

Praha, Czech Republic

Institute of Physics, Academy of Sciences of the Czech Republic Rodová

Praha, Czech Republic

Institute of Physics, Academy of Sciences of the Czech Republic Kozisek

Praha, Czech Republic

Determination of Time Characteristics of Solidification of Supercooled Halide Melt from Measurements of its Electrical Conductivity Origin of supercoolability in metallic and halide melts is discussed. While the level of supercooling in metals is closely connected with the structural incompatibilities between the molten state and product crystal, respectively, the supercoolability of halide melts is caused by their strong complexforming nature. The investigation of processes in supercooled melts is important, because the supercooling of melt strongly influences the nucleation and growth of crystals from the melt and their final quality. Electrical resistance is a suitable quantity to study the solidification of melts, since it can be measured both in liquid state (including supercooled melt) and during the solidification. The early stage of solidification of PbBr2 melt was analyzed within the context of nonstationary nucleation theory. The proposed model describes the time dependence of electrical conductivity of the melt. The time lag of nucleation is calculated and compared with the experimental value. Metallic melts Halide melts,Supercoolability Electrical Conductivity https://mpm.spbstu.ru/article/2003.8.5/ MPM_6_1_P05.pdf

RAR RUS 49-57 The University of Tokushima Mori

Tokushima,Japan

University of Kansas Laird

Lawrence, USA

Tokyo University of Agriculture and Technology Kangawa

Tokyo, Japan

Mie University Ito

Mie, Japan

Tokyo University of Agriculture and Technology Koukitu

Tokyo, Japan

Semigrand Canonical Monte Carlo Simulation with Gibbs-Duhem Integration Technique for Alloy Phase Diagram Formulation is given for the Gibbs-Duhem integration (GDI) method in the semigrand canonical (SGC) ensemble, in which the total number of particles N is fixed with the specified chemical potential differences between species ∆µi (≡µi -∆µ1 ;i =2,3,...). Demonstration of the SGC Monte Carlo simulation with the GDI technique is given for a pseudo-binary semiconductor alloy, Inx Ga1-x N. Gibbs-Duhem integration method GDI technique Monte Carlo simulation https://mpm.spbstu.ru/article/2003.8.6/ MPM_6_1_P06.pdf

RAR RUS 58-62 St.Petersburg State Technological Institute Belyaev

St.Petersburg, Russia

St.Petersburg State Technological Institute Rubets

St.Petersburg, Russia

St.Petersburg State Technological Institute Kalinkin

St.Petersburg, Russia

"Solution Heteroepitaxy" in the Formation of Epitaxial Films of II-VI Compounds under Highly Nonequilibrium Conditions Initial stages of the epitaxial growth of CdTe and CdS film on substrates cooled to the temperatures below 0 °C are experimentally investigated. Electron diffraction patterns corresponding to the early stages of growth and photographs of the surface are presented. The experimentally revealed features (island size 20-25 nm, a δ-function size distribution of the islands, and a monotonic orientation process of the islands) are explained in the framework of a phenomenological theory of heterophase fluctuations and nucleation with the use of migration of solitons initiated by the misfit dislocations of crystal lattices. CdTe film CdS film Heteroepitaxy https://mpm.spbstu.ru/article/2003.8.7/ MPM_6_1_P07.pdf

RAR RUS 63-66 Theoretical Physics Department Nizhny Novgorod University Maksimov

Nizhny Novgorod, Russia

University of Tokushima Shirazawa

Tokushima, Japan

The University of Tokushima Mori

Tokushima,Japan

Multilayer Model of Solid-Liquid Interface: Metastability Limits and Non-Equilibrium Characteristics A multilayer mean-field model of a solid-liquid interface (SLI) is studied. The interface stability diagram is constructed on the basis of both discrete and the continuous approach taking into account the multistability phenomenon. An analytical expression is derived for the demarcation line, which separates two different SLI propagation modes: a barrier-controlled growth and an activationless one. The dynamics of the SLI propagation at high supercooling conditions is considered, the SLI runaway phenomenon accompanied by the SLI kinetical roughening is predicted. Multilayer Model Solid-Liquid Interface Metastability Limits Non-Equilibrium Characteristics https://mpm.spbstu.ru/article/2003.8.8/ MPM_6_1_P08.pdf

RAR RUS 67-70 Ecole Centrale de Lyon Scorretti

Ecully, France

Centre national de la recherche scientifique Santucci

Lyon Cedex, France

Université de Polynésie Française Guarino

Tahiti, French Polynesia

Centre national de la recherche scientifique Vanel

Lyon Cedex, France

Centre national de la recherche scientifique Ciliberto

Lyon Cedex, France

Failure Time of Elastic Materials Submitted to a Constant Load We present a model of delayed fracture in elastic materials, which takes into account the non-reversibility of the system. The results show reasonable agreement both with existing experimental data and 2-D numerical simulations on mode-I fracture. Failure Elastic materials Modelling https://mpm.spbstu.ru/article/2003.8.9/ MPM_6_1_P09.pdf

RAR RUS 71-79 Institute of Problems of Mechanical Engineering RAS Aero

St.Petersburg, Russia

Highly Non-Linear Theory of Bifurcation Transformations of Crystalline Lattice Structures A highly-nonlinear theory is elaborated which describes elastic and inelastic phenomena in media with complicated lattice structure consisting of two sublattices. In the framework of this approach, the standard linear theory of acoustic and optic oscillations of a complicated lattice is generalized, taking into account internal translational symmetry of relative shear of the sublattices taken into account. As a result, the interaction between the sublattices is characterized in terms of a non-linear periodic force described, in particular, as sine of relative shear of two atoms belonging to an elementary cell. The corresponding equations in the case of solids without a central symmetry contain terms that describe the interatomic interactions. We have the situation with quasistatic loading of solids. The dependence of effective stresses on macroscopic strains is found which has a bifurcation point responsible for a structural transformation of the twinning type. It is shown that the transformation is related to a transformation of the interatomic interaction potential, the namely occurrence of both an additional minimum of the potential and a new structure (which has mirror symmetry relative to the initial structure. Crystalline Lattice Structures Highly-nonlinear theory Elastic and inelastic phenomena https://mpm.spbstu.ru/article/2003.8.10/ MPM_6_1_P10.pdf