Theoretical study of kaolinite

Kaolin clays are layer aluminosilicates showing a large variety of physicochemical properties. The most common clay mineral, kaolinite, has been widely studied and it crystallizes in space group P1. We used the ab initio method in order to study kaolinite structure. The RHF calculations were performed at different basis set levels and pseudopotentials (3-21G*, 6-31G, DZP, TZV, CEP-31G, LANL2DZ, and SHC). The two-layer Oniom calculation was applied. The RHF and B3LYP at the 3-21G* basis set level were used for the high-layer Oniom and the Dreiding force field was used for the low-layer Oniom. The hydrogen positions were completely optimized. The geometry of cluster models is taken from the crystallographic data. Vibrational frequencies of hydrogen stretching are also reported. (c) 2005 Wiley Periodicals, Inc.