FIRST-PRINCIPLES STUDY ON THE GEOMETRY AND STABILITY OF HYDROGEN ON THE Ta(001)(1 × 1) SURFACE

The adsorption of hydrogen atoms on the Ta(001)(1 × 1) surface is studied by first-principles density functional calculations within the generalized gradient approximation. It turns out that at 1 ML, coverage bridge site is energetically preferred over three-fold hollow site. This result does not support a recent LEED and HREELS observation that three-fold hollow site was preferred. The layer separation between the H atom and the topmost Ta atom is 1.12 Å and 0.55 Å for bridge and three-fold hollow site, respectively. Atomic distance between the H atom and the first layer Ta atom is 1.998 Å for bridge and 2.06 Å for three-fold site. The structural and energetic properties of H/W(100)(1 × 1) have been calculated. The results are shown to be in excellent agreement with available experimental and theoretical analysis. We find that the adsorption behavior of hydrogen on Ta(001)(1 × 1) surface is very similar to that of H/W(100) system.