State of the art ab initio calculations were used to deduce the diffusion properties of He in W. The calculated migration energy of He was very low (around 0.06eV). This value was much lower than the experimental field-ion microscopy results which led to a migration energy of 0.24 to 0.32eV. The reason for this discrepancy was the high propensity for He to form He-He clusters characterized by a very large binding energy of the order of 1eV. Such a large binding energy indicated that He atoms could be trapped by other He atoms and could explain the formation of He blisters close to the surface of He implanted tungsten.

Migration Energy of He in W Revisited by ab initio Calculations. C.S.Becquart, C.Domain: Physical Review Letters, 2006, 97[19], 196402 (4pp)