The vacancy and H interactions in bcc Nb are important due to their implication in understanding of the H induced damage of Nb metallic membrane used in H2 separation and purification application.Using density functional theory,the vacancy formation energy and vacancy(Vac)-H interaction energies are calculated.The results show that vacancies have a strong trapping effect on H atoms,which lowers the formation energy of Vac-nH clusters substantially.The concentration of Vac-nH clusters is evaluated using a statistical model and the dependence of the concentration on the H-to-M ratio is obtained.It is shown that the concentration of the Vac-nH clusters can be as high as 10-3 at 573K,i.e.one Vac-nH cluster per 1000 atoms,in good agreement with the experimental observations.%The vacancy and H interactions in bcc Nb are important due to their implication in understanding of the H induced damage of Nb metallic membrane used in Hi separation and purification application. Using density functional theory, the vacancy formation energy and vacancy (Vac)-H interaction energies are calculated. The results show that vacancies have a strong trapping effect on H atoms, which lowers the formation energy of Vac-nH clusters substantially. The concentration of Vac-nH clusters is evaluated using a statistical model and the dependence of the concentration on the H-tc-M ratio is obtained, ft is shown that the concentration of the Vac-nH clusters can be as high as 10~3 at 573K, I.e. One Vac-nH cluster per 1000 atoms, in good agreement with the experimental observations.
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