Thermodynamic properties of vacancy-hydrogen complex in tungsten

Formation energies for vacancy-hydrogen (V-H) complexes in tungsten (W) are calculated in terms of first-principles calculations. The dependence of concentration of V-H complexes on temperature and local H concentration is estimated assuming thermal equilibrium. It has been reported that a maximum of 12 H atoms are accommodated in a W monovacancy at 0 K. However, major monovacancies trap six H atoms in finite temperature.