2008 Volume 57 Issue 8 Pages 774-779
Hydrogen diffusion process in nickel crystal is examined by using molecular dynamics method. Firstly the diffusion coeffcients of hydrogen at several temperature are evaluated. The diffusion coeffcients 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 coeffcients 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. Considering the energy landscape between the stable site and transition site including hydrogen, the activation energy obtained by nudged elastic band method is modified to be close to that obtained by mean square displacements.
