Atomic scale modelling methods were used to study the change in vacancy population when H was introduced into the W bulk matrix. Vacancy defects were predicted to predominate in pure W, and the vacancy concentration was expected to be very small. A mechanism whereby H solutes facilitated vacancy formation was outlined and a single H interstitial was predicted to reduce the vacancy formation energy from 2.95 to 2.23eV. Clustering of H interstitials in W was predicted to be unfavourable without a W vacancy. H was also shown to affect the vacancy binding characteristics in W and change the behaviour from a repelling interaction in pure W; retarding the formation of small vacancy clusters, to an attractive interaction when vacancy-H clusters were considered.

Hydrogen Induced Vacancy Formation in Tungsten. S.C.Middleburgh, R.E.Voskoboinikov, M.C.Guenette, D.P.Riley: Journal of Nuclear Materials, 2014, 448[1-3], 270-5