We present the results of ab initio molecular dynamics simulations on the structural and dynamical properties of the Bronsted acid site in a zeolitic cage. The protonated sodalite H[AlSi11O24] is the case studied, and the sodium sodalite is the reference unprotonated zeolite. The comparison between the geometrical parameters calculated for these two sodalites shows that the formation of an O-H bond gives rise to a significant local distortion of the framework geometry. Moreover, an equilibrium between partially ionic and covalent structures in the T-O bonds of the acid site is deduced from our calculations. We have found that the OH bond oscillates in and out of the plane of the 6-T-ring. The analysis of the simulated vibrational spectra has allowed us to assign the bands relative to the O-H in-plane and out-of-plane bending modes and confirms that these bands overlap with the framework modes.

Structure and dynamics of a Bronsted acid site in a zeolite: An ab initio study of hydrogen sodalite

FOIS, ETTORE SILVESTRO;GAMBA, ALDO;TABACCHI, GLORIA
1998-01-01

Abstract

We present the results of ab initio molecular dynamics simulations on the structural and dynamical properties of the Bronsted acid site in a zeolitic cage. The protonated sodalite H[AlSi11O24] is the case studied, and the sodium sodalite is the reference unprotonated zeolite. The comparison between the geometrical parameters calculated for these two sodalites shows that the formation of an O-H bond gives rise to a significant local distortion of the framework geometry. Moreover, an equilibrium between partially ionic and covalent structures in the T-O bonds of the acid site is deduced from our calculations. We have found that the OH bond oscillates in and out of the plane of the 6-T-ring. The analysis of the simulated vibrational spectra has allowed us to assign the bands relative to the O-H in-plane and out-of-plane bending modes and confirms that these bands overlap with the framework modes.
1998
FIRST PRINCIPLES MOLECULAR-DYNAMICS; ZEOLITES; DFT; BRONSTED ACID SITE; SPECTROSCOPY
Fois, ETTORE SILVESTRO; Gamba, Aldo; Tabacchi, Gloria
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/1711185
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