Helium cluster dissolution in molybdenum

Helium retention and diffusion in molybdenum is studied on an atomistic scale with ab initio methods. The thermal stability of helium-vacancy clusters is quantified within the framework of density functional theory. Calculated helium emission rates are used to derive a desorption spectrum which is compared with experimental results. The agreement between the current calculations and available experiments is satisfactory except in the high temperature end of the spectrum. The current results indicate that above 1100 K He migration is assisted by lattice defects such as vacancies, rather than through interstitial diffusion.