Vibrational spectra of aluminosilicate structural clusters

In the work vibrational spectra have been used to describe the framework aluminosilicate structures. Results of spectra calculations carried out for isolated, overtetrahedral structural units which occur in silicates and aluminosilicates are presented. Clusters composed of single and double silico- and alumino-oxygen rings with various numbers of members (4 and 6) containing terminal hydrogen atoms have been chosen for calculations. These clusters have constituted the model analogues of secondary building units (SBU) existing in real zeolite structures. The units selected for calculations have differed in the degree of substitution of silicon atoms with aluminum ones in tetrahedral positions. Visualization of individual vibrations performed has facilitated the band assignments. The results obtained have been used in the interpretation of experimental framework silicates (zeolites) spectra containing the same types of SBU in their structures. The spectra have been analyzed mainly in the ring vibrations region with the aim to determine the influence of aluminum on the spectrum. (C) 2004 Elsevier B.V. All rights reserved.