Model for Molecular Interactions in Helicoidal Cavities

Abstract

A Fourier transform procedure using curvilinear coordinates is developed to determine the interaction potential between a molecule and a helicoidal cavity. When the molecular orientation is free inside the cavity, straightforward criteria for the applicability of the continuum approximation and the molecular confinement along the cavity axis are obtained. At low temperature, the molecule does not rotate freely, being generally trapped in potential wells outside the helix axis and numerical calculations are required to verify whether these criteria hold. An application to N₂ trapped in an AlPO₄-5 cavity shows that the molecule center of mass is confined close to the cavity axis with the molecular axis collinear to the cavity axis.