Strain-induced variation of electronic structure of helium in tungsten and its effects on dissolution and diffusion

We have investigated the effects of strain on the dissolution and diffusion properties of helium (He) in tungsten (W) using a first-principles method. We show that the solubility and diffusion of He can be enhanced (suppressed) with increasing tensile (compressive) strain. This can be attributed to the variation of the effective volume and the p-projected DOS of He induced by the strain. We demonstrate that the strong electronic interaction between He and W atoms plays a key role in the poor solubility of He in W. The tetrahedral interstitial site is always the preferred site of He under all strains. The same rule is believed to hold for other inert gas elements in strained W.