A new empirical potential for zeolite with variable Si/Al ratio: Simulations vs. experiments

A new empirical potential for zeolite framework is proposed as a function of Si/Al ratio. The potential is able to reproduce the variation in the lattice parameter with Si/Al ratio for faujasite obtained from literature and experiments reported in this work. We also report results of calculation with the proposed potential on zeolite A. Maximum deviation is 2.11% which is for Si/Al = 1.18. The atomic positions are within 10⁻⁴ of the experimental crystallographic positions. It is also able to reproduce the pressure-volume relationship and isothermal compressibility. Experimental heat of adsorption of methane in faujasite as well as the adsorption isotherms are also reproduced well. Infra-red spectra for siliceous faujasite shows good agreement with experimental spectra. It is shown that the distribution of aluminum atoms in the lattice has only a marginal role in the value of the lattice parameter.