Translational-orientational coupling during passage of methane through thebottleneck in zeolite A

Diffusion of a five-site model of methane within porous zeolite A has been investigated by molecular dynamics simulation using potential-available in the literature. Equilibrium and dynamical quantities especially those relat ing to the orientational degrees of freedom of methane have been computed. Methane exhibits interesting orientational preference during intercage diff usion through the eight-membered window which is the rate determining step for diffusion. A predominance of (2+2) orientation-in place of (1+3) orient ation is seen suggesting a strong translational-orientational coupling. Thi s suggests that orientational motion might strongly influence the translati onal diffusivity of methane. (C) 2001 American Institute of Physics.