The effect of low-angle grain boundary with extrinsic dislocation on hydrogen retention and transportation in Tungsten

Hydrogen (H) retention and transportation are two critical issues relating to the safe operation of future fusion reactors, and the crystal defects play key roles in the two issues. In the present work the effect of low-angle grain boundary with extrinsic dislocation on H retention and transport in tungsten was investigated using molecular dynamics method. The stress fields of low-angle grain boundary with extrinsic dislocation can be deemed as superposition of the stress field of a disclination dipole and that of the dislocations, resulting in long-range stress field around the low-angle grain boundary. Interaction energy map of H reveals that the dislocation at the negative disclination core can serve as the most efficient trapping site for H among all the dislocations, which is further confirmed by dynamic simulation. Finally, H transportation capability of the low-angle grain boundary was studied by calculation of diffusion coefficients and energy barriers of H along dislocation lines, it is found that the dislocation at the negative disclination core is also an efficient nanochannel for H transportation. The present work provided us a deep insight into H retention and transport in tungsten.