Vacancy trapping behaviors of hydrogen in Ti3SiC2: A first-principles study

The trapping behaviors of hydrogen (H) in MAX phase material Ti3SiC2 have been investigated using a first-principles method with a zero point energy (ZPE) correction. Our calculated result shows that a single H atom is energetically favorable to reside near the Si-vacancy, with lower solution energy than that of the interstitial positions. The Si vacancy has the strong ability for capturing H atoms. Up to five H atoms can be trapped around by a Si vacancy without H-2 molecules formation, due to the repulsive interaction between H atoms. Meanwhile, the diffusion barrier for a H atom from an interstitial site to a Si vacancy is 1.17 eV, much larger than that in metals, indicating that to some extent H atoms cannot easily migrate or aggregate to form bubble in Ti3SiC2. (C) 2013 Elsevier B.V. All rights reserved.