DENSITY-FUNCTIONAL STUDY OF HYDROGEN-BONDED SYSTEMS - FROM GAS-PHASE ADDUCTS TO CATALYTICALLY RELEVANT SYSTEMS

In this note, the performance of methods based on density functional t heory (DFT) to deal with hydrogen bonding interactions (HBI) is addres sed by comparing geometries, harmonic vibrations and binding energies with those obtained by well-established ab initio techniques on the ga s phase adducts (FH)(2), FH/CO and FH/NH3. Anharmonic F-H stretching m ode was also studied in detail. The best combination of functional and basis set is selected and has then been used to model the isolated hy droxyl groups at the silica surface (using H3SiOH (SIL)) and the Brons ted site present in the zeolite cavities (using H3Si(OH)AlH3 (BRO)), b oth free and in interaction with NH3, H2O and CO molecules. Comparison with MP2 and available experimental data is discussed.