Structure, stability and diffusion of hydrogen in tungsten: A first-principles study

Molecular dynamics study of grain boundary diffusion of hydrogen in tungsten

“…from a tetrahedral interstitial positions to an octahedral interstitial position have not been observed as first order transitions. This result is supported by several recent density functional theory studies [17,27,28,29] which also conclude that the energetically preferred migration path of hydrogen in single crystalline tungsten is via tetrahedral interstitial positions -although the derived activation energies in these DFT computations differ by almost 100%. Experimentally, ion-channeling experiments found that interstitial hydrogen in single-crystal tungsten sits at tetrahedral sites [30] -a result which is also in favor of a migration via tetrahedral interstitial positions.…”

Mechanism of vacancy formation induced by hydrogen in tungsten

“…Hydrogen atoms are randomly distributed in the tetrahedral sites which are the favorable sites for hydrogen in bulk tungsten 29 with the concentrations 20 at.% and 30 at.%. The simulation temperatures range from 600 K to 1500 K. The system is firstly relaxed for 10 ps at 0 K, and then the temperature is slowly increased with the rate of 0.1 K/fs to the desired values and kept constant afterwards.…”

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

“…Both DFT and MD indicated the presence of a weakly bound state for two H atoms at a separation of about 2.2 Å, but the binding energy was so low (DFT gave less than 0.1 eV, MD gave 0.3 eV) that it cannot bind the H atoms for significant times even at 300 K [124]. Similar results were obtained by Liu et al [125], obtaining a binding energy between two H atoms of 0.02 eV by means of DFT calculations.…”

“…Note that pure H clusters (H n ) cannot be formed due to the large repulsive energy between H atoms, as has extensively been reported [124,125]. Thus, the clusters that can be formed are pure vacancy clusters (V m ), pure SIA clusters (I m ) and mixed He n V m and He n I m clusters.…”