Density functional theory study of H and H2 interacting with NiAl(110)

RIVIÈRE, P.; BUSNENGO, H.F.; MARTÍN, F.

JOURNAL OF CHEMICAL PHYSICS

Año: 2004 vol. 121 p. 751 - 760

0021-9606

We present results of extensive density functional theory DFT calculations for H and H2 interacting with NiAl(110). Continuous representations of the full dimensional potential energysurface PES for the H/NiAl(110) and H2/NiAl(110) systems are obtained by interpolation of the DFT results using the corrugation reducing procedure. We find a minimum activation energy barrierof 300 meV for dissociative adsorption of H2, which is consistent with the energy threshold obtained in molecular beam experiments for H2(v=0). We explain vibrational enhancement observed in experiments as the consequence of vibrational softening in the entrance channel over the most reactive surface site. The H2/NiAl(110) PES shows a high surface site selectivity: for energiesup to 0.1 eV above threshold, H2 adsorption can only take place around top-Ni sites within a circle of radius 0.3 Å . A strong energetic corrugation is observed: energy barriers for dissociation vary by more than 1 eV between the most and the least reactive sites. In contrast, geometric corrugation is much less pronounced and comparable to that of low index single metal surfaces like Cu or Pt.