Hydrogen Interactions with a Pd4 Cluster: Triplet and Singlet States and Transition Probability

Abstract

The DFT method is used to analyze the singlet and triplet PES cross-sections for a number of reaction pathways of the interaction between a hydrogen molecule and a palladium tetramer. Stationary points characterizing stable singlet and triplet complexes and transition states are determined. Predissociated Pd4H2 complexes with binding energies of 5.0−6.4 kcal/mol are formed without an activation barrier at any initial orientation of reactants in the ground triplet state. The dissociated triplet complexes with adsorption energy of 4.7−8.4 kcal/mol are separated from the predissociated structures by the barrier of 11 kcal/mol. The dissociated singlet structures with hydrogen atoms located in two 3-fold positions and in the bridge positions on nonintersecting Pd−Pd bonds have the same binding energy of 22.1 kcal/mol and correspond to the ground state of the Pd4H2 system. Several more local minima corresponding to dissociated and nondissociated H−H bonds are found on the singlet PES. In contrast to the low-ind...