Computer Simulation of the Location of Para-Xylene in Silicalite

The method of atom-atom potentials has been applied to the localisation of para-xylene molecules within the channels and intersections of silicalite. Two minima were found at the intersection, with interaction energies of −82 and −80 kJmol−1 respectively. These two positions are in good agreement with the results of a recent, room temperature powder X-ray diffraction study. A third, slightly deeper minimum (interaction energy −85kJmol−1) was located in the straight channels but was not occupied in the X-ray diffraction study. This result has been explained by considering entropic effects.