Melting Dramatically Enhances the Reactivity of Aluminum Nanoclusters

The kinetic energy threshold for chemisorption of N-2 on Al-100(+) has been measured as a function of the nanocluster's temperature from 440 to 790 K. When the Al-100(+) cluster melts at 620-660 K, the threshold drops by similar to 1 eV (similar to 96 kJ/mol). A decrease in the activation energy of this magnitude causes a 10(8)-fold increase in the reaction rate at the melting temperature. The decrease in the activation energy may result from the mobility of the surface atoms on the liquid cluster, which allows them to move to a lower energy arrangement as the N-2 approaches.