  We investigate the effects of "dynamic structural disorder" (DSD) on the
behavior of supported nano-scale catalysts. DSD refers to the intrinsic
fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to
bulk materials, nano-scale systems exhibit substantial fluctuations in energy,
charge, and other extensive quantities as well as large surface effects. The
DSD is driven by the stochastic librational motion of the center of mass and
fluxional bonding at the nanoparticle surface due to thermal coupling with the
substrate. Our approach for calculating DSD is based on a combination of
statistical mechanics, transient coupled-oscillator models, and real-time
DFT/MD simulations. This approach treats thermal and dynamic effects over
multiple time-scales, including bond-stretching and -bending vibrations, DSD,
and transient tethering to the substrate at longer ps time-scales. Model
calculations of molecule-cluster interactions and molecular dissociation
reaction paths are presented in which the reactant molecules are adsorbed on
the surface of dynamically sampled clusters. This model suggests that DSD
affects both the prefactors and distribution of energy barriers in reaction
rates, and thus can strongly affect catalytic activity at the nano-scale.
