We plan to study nonlinear behavior in a realistic system of importance for catalysis by use of molecular dynamics and ab initio methods. During the last century, physics has mainly been dominated by linear concepts. The awareness that nonlinear effects ar e important is relatively new. One decade of mainly theoretical research has discovered many new phenomena that contradict our well established physical intuition. Among these are the possible existence of spatially time-periodic localized modes, also call ed discrete breathers, that can occur when locally a fairly large amount of energy is released in a crystal. These modes have been shown to have a macroscopic lifetime and are relatively stable also at non-zero temperature. Therefore, the existence of disc rete breathers will prevent the system, for a period of time, to relax in its thermodynamic equilibrium, and long-lived "hot spots" may be left behind. Contrary to previous studies, we will study these nonlinear phenomena in a realistic case rather than si mplified theoretical models. The system of interest will be hydrogen adsorbed on a palladium surface, an important topic in surface catalysis. We will study the possible existence of discrete breathers on the palladium surface, and if they could be created by the desorption of hydrogen or by a surface chemical reaction. Visa versa, we will investigate how the existence of discrete breathers can influence surface physics (adsorption/ desorption rates, diffusion) and surface catalysis. A successful completion of this project could give one of the first proofs for the occurrence of discrete breathers in realistic systems. Moreover, this project could give complete new insights for surface catalysis with all kinds of potential applications.
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