Kinetic Monte Carlo simulation on influence of vacancy on hydrogen diffusivity in tungsten

Kinetic Mote Carlo (KMC) simulations are performed to quantify the influence of trap in hydrogen diffusivity in tungsten. As a typical trap, mono-vacancy is considered in the simulation. Experimental results reported by Frauenfelder are nicely reproduced when hydrogen concentration and trap concentration expected in the experiment are employed in the simulation. The effective diffusivity of hydrogen is evidently decreased by traps even at high temperatures like 1300 K. These results suggest that only high-temperature experimental data, which are not significantly affected by traps, should be fitted to, in order to derive the true hydrogen diffusivity from experiments. Therefore, we recommend D=1.58×10−7exp(−0.25eV/kT) m2 s−1 as the equation for hydrogen diffusion coefficient in tungsten, which was obtained by fitting only to experimental data at 1500-2400 K by Heinola and Ahlgren, rather than the most cited equation D=4.1×10−7exp(−0.39eV/kT) m2 s−1, which was obtained by fitting to all experimental data at 1100-2400 K including some data that should be affected by traps.