Quantum Mechanics of Hydrogen on Nickel and Palladium Clusters

Within the broad class of metal-hydrogen systems, clusters are of particular importance. Their high surface to volume ratio makes them ideal candidates for catalytic applications. Surface and bulk studies have shown that transport and vibrational spectroscopy of hydrogen are very sensitive to substrate structure. The wide variety of geometries exhibited by clusters offers a noteworthy opportunity to examine the effect of substrate geometry on hydrogen. Further, hydrogen’s small mass and uniquely large isotopic variation gives rise to a number of intrinsically quantum mechanical effects. For example, inverse isotope effects have been observed for hydrogen chemisorption on palladium clusters. Comparing classical and quantum mechanical Monte Carlo methods, the effects of quantum mechanics on cluster structure, population distribution, vibrational spectra, and rates for hydrogen motion are discussed for a single hydrogen on nickel and palladium clusters.