Kinetic Monte Carlo code development and application on the formation of hydrogen-vacancy clusters in tungsten

We have developed an object kinetic Monte Carlo（OKMC）code and simulated hydrogen-vacancy clustering behavior and dependence on temperature and hydrogen-vacancy ratio in tungsten.For each of the temperatures we simulated from 300 K to1000 K,H;V clusters with smaller n form before those with larger n.The elevating temperature leads to a decrease in hydrogen vacancies:H;V and H;V clusters dominate at 300 K and 600 K,whereas H;V,H;V,and H;V clusters dominate when the temperature reaches 1000 K.Furthermore,only H;V clusters with smaller n formed when a lower hydrogen-vacancy ratio was used due to insufficient availability of hydrogen atoms to occupy vacancies.The results suggest hydrogen emission occurs very rarely at lower temperatures,while higher temperatures facilitate the dissociation of hydrogen from H;V clusters.