Stress-induced hydrogen self-trapping in tungsten

The molecular dynamics simulations of trapping of hydrogen atoms in tungsten are presented. The simulations reveal formation of platelet-like structures of self-trapped hydrogen induced by stresses in tungsten, in particular, those produced by dislocations, at the interstitial hydrogen concentrations at.%. The spontaneous hydrogen platelet formation in absence of dislocations and external stresses has been also observed at the higher hydrogen concentrations at.%. It is shown that the platelets can retain substantial quantities of hydrogen, exceeding trapping capacity of other non-cavity defects in tungsten. The properties of the hydrogen platelets formed in tungsten under various conditions are assessed and a formation mechanism is proposed. A model of hydrogen retention by the dislocation-induced structures is also presented, which describes retained quantities and outgassing dynamics of hydrogen in plasma exposed tungsten samples. (paper)