A DENSITY-FUNCTIONAL STUDY OF CLUSTER REACTIVITY .3. NH3 ON A FREE GA5AS5+ CATIONIC CLUSTER

Ammonia chemisorption on a small and positively charged gallium arseni de cluster in the gas phase has been investigated using density-functi onal methods. The reactivity at various cluster sites are characterize d in terms of binding energy and charge transfer from the adsorbate to the cluster with a strong correlation shown between the latter two: q uantities. The calculations show a strong dependence of the reactivity of the cluster on its charge state. Ionizing the bare cluster to a ca tionic charge state enables multiple chemisorption of ammonia, which i s much less favored by a neutral cluster and can be prohibited on a ne gatively charged cluster. (C) 1996 American Institute of Physics.