Characterization of molecular cluster diffusion in AlPO4-5 using molecular dynamics

Recent studies of single-file diffusion in AlPO4-5 showed that diffusion of adsorbed molecules can occur by a surprising mechanism, concerted diffusion of weakly bound molecular clusters [D.S. Sholl and K.A. Fichthorn, Phys. Rev. Lett. 79 (1997) 3569]. In this Letter, molecular dynamics methods allowing metastable adsorbed clusters to be studied at arbitrary temperatures are introduced. These methods are used to give the first detailed characterization of the diffusion and dissociation kinetics of isolated SF6 and CF4 clusters containing up to 18 molecules adsorbed in AlPO4-5 pores. The evolution of these clusters is dominated by the existence of concerted mechanisms for cluster motion.