Molecular dynamics studies of low-energy atomic hydrogen cumulative bombardment on tungsten surface

Applicability of tungsten (W) in divertor regions which are exposed to high flux hydrogen (H) isotope with the energy below 100 eV, is concerned. In this study, the cumulative bombardment of low-energy H atoms on W surface was investigated by molecular dynamics (MD) simulations. For the sake of comparison, the reflection and the retention of the incident H atoms were also calculated and analyzed by the Monte Carlo (MC) method based on the binary collision (BC) approximation and the analytical method based on the bipartition model (BPM). It was found that in addition to the reflection of the incident H atoms, some of the H atoms can implant into the substrate and penetrate from the bottom surface of the substrate due to the channeling effect. The channeling effect mainly contributes to the difference of the distribution of H projectiles, since the structure of substrate in MD is crystal while that in the other two methods is usually homogeneous amorphous. As expected, the point defects (including sputtering atoms) were not observed in all simulations since the energy projectile is below the threshold displacement energy.