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

Abstract

In this work, we combine Density Functional Theory data with a Thermodynamic and a kinetic model to determine the total concentration of hydrogen implanted in the sub-surface of tungsten exposed to a hydrogen flux. The sub-surface hydrogen concentration is calculated given a flux of hydrogen, a temperature of implantation, and the energy of the incoming hydrogen ions as independent variables. This global model is built step by step; an equilibrium between atomic hydrogen within bulk tungsten and a molecular hydrogen gas phase is first considered, and the calculated solubility is compared with experimental results.Subsequently, a kinetic model is used to determine the chemical potential for hydrogen in the sub-surface of tungsten. Combining both these models, two regimes are established in which hydrogen is preferentially trapped at either interstitial sites or in vacancies. We deduce from our model that the existence of these two regimes is driven by the temperature of the implanted tungsten sample; above a threshold or transition temperature is the interstitial regime, below is the vacancy regime in which super-saturated layers form within tenths of angstrom below the surface. A simple analytical expression is derived for the co-existence of the two regimes depending on the implantation temperature, the incident energy and the flux of the hydrogen ions which we use to plot the corresponding phase diagram.

Parametric study of hydrogenic inventory in the ITER divertor based on machine learning

“…In the following, the concentration on was set to for the kinetics involved are really fast (see appendix of 27 ) and is small compared to the monoblock dimensions.…”

Displacement damage stabilization by hydrogen presence under simultaneous W ion damage and D ion exposure

“…A detailed modelling of the measured TDS spectra together with the corresponding depth profiles is beyond the scope of this publication and will be described in [35]. can be calculated for steady state as [36,37]:…”

Surface coverage dependent mechanisms for the absorption and desorption of hydrogen from the W(1 1 0) and W(1 0 0) surfaces: a density functional theory investigation

“…Elastic Recoil Detection Analysis (ERDA) [21], Low Energy Ion Scattering (LEIS) and Direct Recoil Spectroscopy (DRS) [22][23][24] are also used, mostly to gain information on the surface properties. TDS can access global information related to the binding state of hydrogen in the bulk and on the surface, while ion beam analysis accesses local From the theoretical point of view, calculations and simulations have been carried out from the atomistic scales using Density Functional Theory (DFT) [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and Molecular Dynamics (MD) [39][40][41][42][43], to the macroscopic scale using Kinetic Monte Carlo (KMC) [44][45][46][47] and Macroscopic Rate Equations (MRE) [15,[48][49][50][51][52][53][54][55][56][57][58][59][60]. Combining both these approaches results in the commonly called multi-scale approach, in which KMC [44,…”