Séminaire Théorie

Mardi 16 Décembre 2014 à 14h00.

Atomistic simulations of microstructural defects and their role in H trapping and diffusion

''A correct description of hydrogen diffusion and trapping is prerequisite for understanding the phenomenon of hydrogen embrittlement. The macroscopic H diffusion in bulk materials has been studied extensively in the past both experimentally and theoretically. Nevertheless, the knowledge of microscopic diffusion processes, especially in distorted environments around crystal defects, is still limited. In this study we apply atomistic simulations to investigate the diffusion and trapping of hydrogen in Fe and Ni using accurate first-principles methods based on the density functional theory. Our results show that the diffusion barriers can indeed vary significantly in the vicinity of crystal defects, imperfections and interfaces. The calculations also confirm that a proper treatment of quantum effects is crucial for a reliable theoretical description of H diffusion, in particular for bcc Fe. Several examples of H trapping at grain and phase boundaries will be presented and analyzed.''