Jumras LimtrakulSupa HannongbuaMahidol University2018-08-102018-08-101993-03-11Journal of Molecular Structure: THEOCHEM. Vol.280, No.1 (1993), 139-145016612802-s2.0-0006231349https://repository.li.mahidol.ac.th/handle/20.500.14594/22535The catalytic properties of a free hydroxyl on silica, a zeolite and modified zeolites have been investigated within the framework of the ab initio self-consistent field method. Full optimization of structures has been carried out at DZ, DZP and TZ2P levels of theory; electron correlation contributions were estimated using the MP2 method. On the basis of the charges on the hydroxyl proton, OH bond distance, OH stretching frequencies and the energetics of complexation, the Brønsted acidity of the hydroxyls resulted in the following order: SiOH < SiOHB < SiOHGa < SiOHAl . © 1993.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyChemistryPhysics and AstronomyArticleSCOPUS10.1016/0166-1280(93)87104-L