Energetics and many-particle mechanisms of two-dimensional cluster diffusion on Cu(100) surfaces

We study the energetics and stability of small Cu clusters on Cu(100) surfaces using molecular statics combined with systematic saddle-point search methods. We find several previously overlooked concerted many-particle processes that play an important role in cluster energetics. In particular, for smaller clusters there is an internal atom row shear mechanism that in some cases determines the rate-limiting step for center-of-mass motion. Our results suggest specific reaction paths for experimentally observed cluster diffusion events.Peer reviewe

The method of R-functions in the solution of elastic problems on the basis of reissner`s mixed variational principle

A method is presented for solving boundary-value elastic problems on the basis of the variational–structural method of R-functions and Reissner’s mixed variational principle. A mathematical formulation is given to problems on the deformation of elastic bodies under mixed boundary conditions and bodies interacting with smooth rigid dies. Solutions satisfying all the boundary conditions are proposed. For undetermined components of these solutions, the resolving equations are derived and their properties are studied. A posteriori estimation of numerical solutions is made. As examples, solutions are found to a problem on the stress–strain state of a short cylinder and to a contact problem on a cylinder interacting with a smooth die. A numerical method of solving such problems is analyzed for convergence, and the accuracy of the solutions is estimated

Searching for transition paths in multidimensional space with a fixed repulsive bias potential

An efficient method for searching for transition paths in a multidimensional configuration space is proposed. It is based on using a fixed, locally repulsive bias potential, which forces the system to move from a given initial state to a different final state. This simple method is very effective in determining nearby configurations and possible transition paths for many-particle systems. Once the approximate transition paths are known, the corresponding activation energies can be computed using, e.g., the nudged elastic band method. The usefulness of the present method is demonstrated for both classical and quantum-mechanical systems.Peer reviewe

Minimum energy paths for dislocation nucleation in strained epitaxial layers

We study numerically the minimum energy path and energy barriers for dislocation nucleation in a two-dimensional atomistic model of strained epitaxial layers on a substrate with lattice misfit. Stress relaxation processes from coherent to incoherent states for different transition paths are determined using saddle point search based on a combination of repulsive potential minimization and the Nudged Elastic Band method. The minimum energy barrier leading to a final state with a single misfit dislocation nucleation is determined. A strong tensile-compressive asymmetry is observed. This asymmetry can be understood in terms of the qualitatively different transition paths for the tensile and compressive strains.Peer reviewe

Electronic payment systems in the world and their use in ukraine

У статті розкрито сутність електронних платіжних систем, обґрунтовано переваги їх застосування у міжнародній і вітчизняній практиці, запропоновано заходи щодо поліпшення структури грошового обігу завдяки масовим безготівковим платежам із використанням електронних платіжних систем. The article reveals the essence of electronic payment systems. There are advantages of their use in international and domestic practice. We proposed measures to improve the structure of currency through massive non-cash payments using electronic payment systems

Renal function remains after unilateral total and contralateral partial nephrectomy : an experimental study in pigs using 99mTc-DTPA

Peer reviewe

Chains of Viscoelastic Spheres

Given a chain of viscoelastic spheres with fixed masses of the first and last particles. We raise the question: How to chose the masses of the other particles of the chain to assure maximal energy transfer? The results are compared with a chain of particles for which a constant coefficient of restitution is assumed. Our simple example shows that the assumption of viscoelastic particle properties has not only important consequences for very large systems (see [1]) but leads also to qualitative changes in small systems as compared with particles interacting via a constant restitution coefficient.Comment: 11 pages, 6 figure

Role of concerted atomic movements on the diffusion of small islands on fcc(100) metal surfaces

The master equation formalism is used to analytically calculate the center-of-mass diffusion coefficient for small two-dimensional islands on fcc(100) metal surfaces. We consider the case of Cu on Cu(100) containing up to nine atoms, with energetics obtained from semiempirical interaction potentials. In the case where only single-particle processes are taken into account, the analytic results agree well with previous Monte Carlo simulation data. However, when recently proposed many-particle processes are included, in some cases the diffusion coefficients increase by an order of magnitude at room temperatures. Qualitatively, the oscillatory behavior of diffusion as a function of the island size is not affected by the many-particle processes.Peer reviewe