Communication: First-principles evaluation of alkali ion adsorption and ion exchange in pure silica LTA zeolite.

Using first-principles calculations, we studied the adsorption of alkali ions in pure silica Linde Type A (LTA) zeolite. The probability of adsorbing alkali ions from solution and the driving force for ion exchange between Na and other alkali ions at the different adsorption sites were analyzed. From the calculated ion exchange isotherms, we show that it is possible to exchange Na with K and Rb in water, but that is not the case for systems in a vacuum. We also demonstrate that a solvation model should be used for the accurate representation of ion exchange in an LTA and that dispersion interactions should be introduced with care.