Dissociative adsorption of H-2 on the H/Si(100) surface - The effect of intradimer pi-bonding disruption

We have studied dissociative H-2 adsorption on the H/Si(100) surface by mea ns of pseudopotential density functional theory calculations. This work is directly motivated by the observations of Biederman et al. [Phys. Rev. Lett ., 83, 1810 (1999)]: "H-2 adsorption is significantly promoted in an interd imer configuration of two adjacent singly occupied dimers." We find that th ere is no adsorption barrier on the local site where two quasi-free danglin g bonds are available; the adsorption energy is estimated to be 2.6 eV per H-2 within the local density approximation. We present maximally localized Wannier functions that clearly illustrate the behavior of dangling orbitals upon the approach of H-2. The results suggest that intradimer pi -bonding disruption is crucial for the significant promotion of H-2 adsorption on Si (100). (C) 2001 The Electrochemical Society.