Ab Initio multireference configuration-interaction study of hydrogen molecule activation by Cs-promoted Pt clusters

• Published in: The Journal of chemical physics 2006-01, Vol.124 (2), p.024703-024703-7
• Main Authors: Benitez, J. I., Castillo, S., Poulain, E., Bertin, V.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.2141954

The adsorption of the H 2 molecule on Cs n Pt ( 5 − n ) bcc (111) clusters for Cs ∕ Pt rates of 20%, 40%, and 80% is studied using ab initio multiconfigurational self-consistent field plus multireference configuration-interaction variational and perturbative calculations. The H 2 interaction with the clusters is studied in ground and excited states with geometry optimization, where the hydrogen adsorption takes place by a Pt atom. These calculations are compared with those of H 2 adsorption on Pt 4 . The most stable configurations of CsPt 4 and Cs 2 Pt 3 clusters ( Cs ∕ Pt rates of 20% and 40%) are a doublet and a closed-shell singlet, respectively. Both clusters capture and activate the hydrogen molecule and their behaviors resemble Pt 4 . The H 2 capture distances are, respectively, similar and smaller than Pt 4 capture distances, while the H - H bond dissociation distances are similar and bigger than those of Pt 4 ; however, none of them presents activation barriers. The most stable Cs 4 Pt cluster ( Cs ∕ Pt rate of 80%) is also a closed-shell singlet; it also captures and activates the hydrogen molecule and shows a different behavior as compared with CsPt 4 , Cs 2 Pt 3 , and Pt 4 clusters. The capture distance is quite smaller and is obtained after surmounting an activation barrier. For all clusters studied here, no hydrogen absorption was observed, only the adsorption of H 2 .