Tracer diffusion in ordered lattice-gas systems with defect-controlled transport mechanisms
Tracer diffusion in an ordered two-dimensional lattice-gas system with square lattice symmetry is studied theoretically and by means of computer simulations. It is well known that the ordering with c 2 2 symmetry formed in the vicinity of half-filling of lattice sites is due to strong nearest neighbor repulsive interaction. In this case, the tracer migration occurs mainly by elementary displacements of structural defects. This paper focuses on the dimer transport mechanism which was accounted for with insufficient accuracy in previous publications. The long-time asymptotics of the dimer-tracer correlation function i.e., a three-particle correlation function , which describes concerted tracer-dimer motion, is obtained analytically. We analyze a specific exchange mechanism, relevant to tracer diffusion only. Also, the contribution of generation-recombination jumps to tracer diffusion is taken into account. The theoretical data agree well with the results of intensive Monte Carlo simulations.
Transport of adsorbates at metal surfaces: from thermal migration to hot precursors
Abstract Theoretical aspects and evolution of surface diffusion studies are discussed with an emphasis on non-metallic adsorbates at metal surfaces. A survey of the existing literature is presented with the main experimental results tabulated. (The tables and their updates are available online at http://ipent.epfl.ch/gr_kern/jv_barth/SD_tables.html) Conception, theoretical and experimental work on transient mobility in the adsorption of gases on metal surfaces are summarized.
Influence of the residual stress on the magnetization process in mild steel
The influence of residual stress on the hysteresis properties of mild steel is studied in detail. Magnetic measurements were done in different directions to investigate the stress-induced anisotropy. The hysteresis loops measured in any fixed direction at different levels of deformation crossed at two points known as the coincident points. One possible explanation of this effect is proposed and it makes an assumption about the stress-induced term in the effective field model. Loops measured in different directions at any fixed level of deformation also crossed at two points. It was found that the hysteresis loop follows a very simple formula when changing the direction of the measurement from the easy axis to the hard one. This explained not only the crossing of these loops at the two points but also the results of measurements on ring-shaped samples where all the directions are possible.