Evolution of Small Ti Clusters and the Dissociative Chemisorption of H₂ on Ti

The sequential growth of small titanium clusters with up to 15 atoms and the dissociative chemisorption of H 2 on the minimum energy clusters have been studied within density functional theory under the generalized gradient approximation. It has been found that the low-energy clusters grow three dimensionally from Ti 4 and follow a pentagonal growth pattern. The clusters Ti 7 and Ti 13 show a higher stability than other clusters with a configuration of pentagonal bipyramid and icosahedron structures, respectively. The second difference of binding energy plot indicates that these two clusters are highly stable; this agrees with the experimental collision-induced dissociation studies and previous theoretical calculations. For the first time, a systematic study of chemical reactivity of small Ti n clusters, with n = 2−15, toward dissociative chemisorption of H 2 is performed. It is found that the chemisorption occurs preferentially at the two adjacent edges of any Ti atom. The chemisorption energy as a function of the cluster size shows considerable structural changes in the Ti n clusters due to H 2 dissociation and adsorption, and the chemisorption energy of Ti 13 cluster is found to be the highest.