Computational studies of lithium affinities for zeolitic fragments

In this Letter, we report optimized structures and lithium affinities of a series of anionic zeolitic fragments [H3Al(oCH(3))(x)(OSiH3)(1-x)(-). 2T, H 2Al(OCH3)(x)(OSiH3)(2-x)(-) 3T, Al(OCH3)(x)(OSiH3)(4-x)(-) 5T] that mimic t he charge sites in polyelectrolytes. Ab initio molecular orbital methods at different levels of theory are used. The lithium affinities are much large r than the corresponding sodium affinities, indicating stronger interaction s between lithium cations and these zeolitic fragments. The substitution of silicon by carbon increases the lithium affinity and the effect is general ly larger than in the sodium systems. (C) 2000 Elsevier Science B.V. All ri ghts reserved.