Adsorption isotherm sensitivity to small changes in zeolite structure

Grand canonical Monte Carlo (GCMC) simulations of benzene adsorption in dif ferent ORTHO silicalite structures are analyzed to determine the origin of a surprising factor of 3.1 difference in the Henry's law constants. Results indicate that changes of only tenths of (a) over circle ngstrom in the lat tice oxygen atom positions can reposition the sorbates enough to sizably af fect the electrostatics. The small shifts are magnified by the partial canc ellation of large electrostatics terms on the hydrogen and carbon atoms. Th ese results underscore the need for potential models that include lattice f lexibility and polarizability when the sorbates are tightly fitting, as wel l as accurate crystallographic structures. (C) 1999 Elsevier Science B.V. A ll rights reserved.