Dissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals

Abstract

First-principles calculations are performed to investigate the dissolving, trapping and detrapping of H in six bcc (V, Nb, Ta, Cr, Mo, W) and six fcc (Ni, Pd, Pt, Cu, Ag, Au) metals. We find that the zero-point vibrations do not change the site-preference order of H at interstitial sites in these metals except Pt. One vacancy could trap a maximum of 4 H atoms in Au and Pt, 6 H atoms in V, Nb, Ta, Cr, Ni, Pd, Cu and Ag, and 12 H atoms in Mo and W. The zero-point vibrations never change the maximum number of H atoms trapped in a single vacancy in these metals. By calculating the formation energy of vacancy-H (Vac-Hn) complex, the superabundant vacancy in V, Nb, Ta, Pd and Ni is demonstrated to be much more easily formed than in the other metals, which has been found in many metals including Pd, Ni and Nb experimentally. Besides, we find that it is most energetically favorable to form Vac-H1 complex in Pt, Cu, Ag and Au, Vac-H4 in Cr, Mo and W, and Vac-H6 in V, Nb, Ta, Pd and Ni. At last, we examine the detrapping behaviors of H atoms in a single vacancy and find that with the heating rate of 10 K/min a vacancy could accommodate 4, 5 and 6 H atoms in Cr, Mo and W at room temperature, respectively. The detrapping temperatures of all H atoms in a single vacancy in V, Nb, Ta, Ni, Pd, Cu and Ag are below room temperature

Hydrogen supersaturated layers in H/D plasma-loaded tungsten: A global model based on thermodynamics, kinetics and density functional theory data

“…We nevertheless used half the energy of a H 2 molecule to calculate e int , e 0 and e j displayed in Table 1. These data are in good agreement with some other ones that can be found in the literature [19][20][21]. For j = 1 to 6, the formation energy of a VH j vacancy requires less energy than the formation of an empty vacancy e 0 ; this energy difference is indeed the driving mechanism that leads to the formation of abundant VH j vacancies.…”

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

“…Furthermore, the detrapping energy of the defect site has been found to be dependent on the number of hydrogen isotopes bound to the tungsten defects site. This behaviour is somehow quite general, since it has been found by DFT for vacancies [14][15][16][17][18][19], dislocations [21] and grain boundaries [21,22] in tungsten, and it has been recently included in MRE model codes by Schmid et al [23] and Hodille et al [9]. The latter implementation used in the present work, called MHIMS-Reservoir [9], can be summarized with the potential energy diagrams of figure 4.…”

“…Then, it has to surmount diffusion barriers E diff to reach the surface, go deeper in the bulk or become trapped in another defect site. For tungsten, the diffusion well corresponds to a tetrahedral interstitial position [14][15][16][17][18][19] while the trapping well depends on the type of defect considered (vacancy, grain boundary site…). Finally, if two hydrogen isotopes reach the surface, they can recombine and form a desorbing molecule.…”

Hydrogen-induced blistering of Mo/Si multilayers: Uptake and distribution

“…The high content in the outermost Mo layer is likely due to trapping in vacancies and voids in the structure. First principle calculations indicate that a single Mo mono-vacancy can accommodate up to 12 H atoms, with the added possibility of H 2 formation [47,48]. Hydrogen accumulated in this way can more readily provide a reservoir to feed blister growth than hydrogen that is chemically bound in the Si layers.…”