Isolated cluster calculations on the hydrogen-bonded complex between a model of acidic sites in zeolites and the ammonia molecule have shown no appreciable difference between the neutral and ionic (proton transferred) forms, although experimental evidence indicates that the latter should be more stable. In the present work we demonstrate that the effect of the crystal field, when considered explicitly in the quantum-chemical calculations, significantly stabilizes the ion-pair form of the complex. The problems associated with the definition of a cluster in a covalently bonded extended system and the inclusion of long-range electrostatic effects are discussed in some detail.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry