The dynamics of the Al 17 − •(H 2 O) 2 system has been studied by means of potential energy surface computations combined with quasiclassical molecular dynamics simulations and transition state theory computations. The complete process of H 2 generation has been analyzed. The system first undergoes water-splitting steps, generating HAl 17 OH − •(H 2 O) and H 2 Al 17 (OH) 2 − species. The cluster flexibility plays a major role in the dynamics, because it allows for a quick allocation of the excess energy of the hydrogen atom that splits from water. The result appears to be that H 2 production is significantly delayed by the complexity of the potential energy surface and the presence of long-lived intermediates. It turns out that the dihydroxyl structures H 2 Al 17 (OH) 2 − can easily undergo further O−H bond breaking to generate the doubleand triple-bridged oxo structures H 3 Al 17 O(OH) − or H 4 Al 17 O 2 −. On the basis of the dynamics computations, new mechanisms for H 2 generation are proposed in which the dioxo structures play an important role. It is also shown that some intermediates have distorted forms of the Al frame that can be traced back to low-lying structures of the Al 17 − cluster. Tunneling does not appear to play a critical role, except in the first reaction steps, the water-splitting processes. The impact of the variation of the total energy of the system on the onset of H 2 production and on the mechanism is discussed. Some conclusions could be applicable to the reaction of many other Al clusters with water.
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