ON THE CLUSTER CONVERGENCE OF CHEMISORPTION ENERGIES

Artikel i vetenskaplig tidskrift, 1988

A new rule is suggested for calculating chemisorption energies using the cluster model. This rule is built on the realization that relatively large clusters (50 atoms and more) often need to be prepared for bonding by making an excitation to a proper bonding state (such a state will always be easily accessible in an infinite cluster). For hydrogen chemisorption, this bonding state must have a singly occupied orbital of the same symmetry as the hydrogen 1 s orbital. The new rule is applied to hydrogen chemisorption in the hollow sites of Ni(100) and Ni(111). When a cluster is prepared in a bonding state, even quite small clusters (≈ 10 atoms) give chemisorption energies in reasonable agreement with experimental surface results.