Adlayer structures of pyridine base molecules over zeolite (010) surfaces:a semi-empirical study based on AFM observations

The molecular array structures and molecular orientations within the adlaye rs of pyridine base molecules (pyridine and beta-picoline) liquid-phase-ads orbed on (010) surfaces of natural zeolites (heulandite and stilbite) deter mined by in situ atomic force microscopy (AFM) were examined by semi-empiri cal molecular orbital calculations. All the adlayers studied possess (quasi -)hexagonal array structures, with different two-dimensional lattice consta nts for different adsorption systems. The AFM-observed array structures wer e close to the calculated energy minima with respect to their unit cell dim ensions, The AFM-observed molecular orientation within the beta-picoline ad layer was also energetically the most favourable among possible molecular o rientations, Molecular tilt angles, which were not determined by AFM, were estimated by the semi-empirical calculations. Copyright (C) 1999 John Wiley & Sons, Ltd.