Europhys. Lett.
Volume 63, Number 4, August 2003
Page(s) 556 - 561
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00566-9
Europhys. Lett., 63 (4) , pp. 556-561 (2003)

Auto-catalytic effect in ammonia dissociation on $\chem{Si(100)}$ surface: First-principles model study

M. Z. Zgierski and Z. K. Smedarchina

Steacie Institute for Molecular Sciences, National Research Council of Canada Ottawa, K1A 0R6 Canada

(Received 28 April 2003; accepted in final form 16 June 2003)

Density functional theory and an approximate instanton method have been applied to calculate absolute rate constants of ammonia dissociation on a model $\chem{Si(100)}$ surface. It is shown that the dissociation is dominated by hydrogen atom tunneling even at room temperature, and that high coverage of the surface, when two ammonia molecules adsorb on the nearest-neighbour $\chem{Si}$ dimers occupying the same row, speeds up the dissociation process. This auto-catalytic effect is attributed to the modification of the buckling of the two $\chem{Si}$ dimers in the presence of a second ammonia molecule.

68.43.Bc - Ab initio calculations of adsorbate structure and reactions.
82.30.Lp - Decomposition reactions (pyrolysis, dissociation, and fragmentation).
82.65.+r - Surface and interface chemistry; heterogeneous catalysis at surfaces.

© EDP Sciences 2003