Ab initio plane-wave electronic structure calculations are widely used in the study of bulk materials. A technique for the projection of plane-wave states onto a localized basis set is used to calculate atomic charges and bond populations by means of Mulliken analysis. We analyze a number of simple bulk crystals and find correlations of overlap population with covalency of bonding and bond strength, and effective valence charge with ionicity of bonding. Thus, we show that the techniques described in this paper may be usefully applied in the field of solid state physics. ͓S0163-1829͑96͒07847-2͔

The methanol to gasoline (MTG) conversion process, using a zeolite catalyst, is of major commercial importance. However, the first step of the reaction, involving methanol adsorption on the zeolite catalyst, is still not well understood. This paper describes first-principles calculations performed on periodic zeolite models to investigate the nature of methanol adsorption. We have examined a number of possible geometries for this adsorption and found that the nature of the adsorbed species can depend on the particular zeolite structure. In more open ring structures, as found in chabazite, the stable form of methanol is found to be protonated, in contrast to results of previous calculations on cluster models. However, in the sodalite structure methanol is found to be simply physisorbed. The vibrational spectra of the adsorbed species have been studied and compared to experimental results. It is found that both chemisorbed methanol and physisorbed methanol give strongly red-shifted O−H stretching frequencies, but the former can be distinguished by the H−O−H bending mode.

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Zeolites are microporous aluminosilicate materials used as industrial catalysts, and there is much interest in understanding their catalytic behavior. The adsorption of methanol in the catalytically active zeolite chabazite and in sodalite was examined by performing ab initio calculations within periodic boundary conditions. A direct correlation between zeolite structure and chemical activation of the adsorbate was found. Methanol was protonated without an activation energy by a Brønsted acid site, provided the molecule was situated in the eight-ring window of chabazite, whereas the same molecule was only physisorbed in more open cage regions, such as those found in sodalite.

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