Dynamics of intercalated molecules. Part 1.—Sorption potentials and structure ‘C24Cs’(CH4)

Abstract

Sorption of methane in the second-stage graphite intercalation compound, ‘C₂₄Cs’, has been explored by calculating molecular translational and rotational potential-energy surfaces, the molecular orientation and the sorption enthalpy in the approximation of a rigid caesium-ion lattice. The molecule sits comfortably in the ([graphic omitted] × [graphic omitted]) caesium layer structure. The translational potential-energy surface and sorption enthalpy are mainly sensitive to van der Waals forces, and three different methane–caesium potentials have been evaluated. The molecular setting angles and barriers to rotation depend more on the electrostatic interactions and in particular the graphite charge distribution, models for which have also been chosen. Detailed predictions of molecular setting angles and site structures are given for ultimate test by diffraction experiments.