Analysis of Hydrogen Diffusion Process and Elementary Process in Nickel Crystal by Molecular Dynamics Simulation
Toshihiko MASAIE, Yusuke DOI and Akihiro NAKATANI
Abstract:Hydrogen diffusion process in nickel crystal is examined by using molecular dynamics method. Firstly the diffusion coefficients of hydrogen at several temperature are evaluated. The diffusion coefficients obtained by using mean square displacements agree well with those obtained by the jump diffusion theory. Considering the correlation factors of hydrogen diffusion, the diffusion coefficients obtained by the jump diffusion theory is more close to that obtained by using mean square displacements. Secondly, the elementary process of hydrogen diffusion is discussed. The activation energy of hydrogen diffusion obtained by using mean square displacements and that obtained by nudged elastic band method are different, since the jump of hyrogen atom to next stable site is finished before the nickel atoms construct the stable structure with transition site including hydrogen. To estimate the energy landscape between the stable site and transition site including hydrogen, the activation energy obtained by nudged elastic band method is close to that obtained by mean square displacements. Key Words:Molecular dynamics, Diffusion, Hydrogen, Elementary process, Mean square displacement, Jump diffusion model, Nudged elastic band method