Effects of the Aluminum Content of a Zeolite
Framework: A DFT/MM Hybrid Approach Based on
Cluster Models Embedded in an Elastic Polarizable
Environment
posted on 2005-05-10, 00:00authored byElena A. Ivanova Shor, Alexei M. Shor, Vladimir A. Nasluzov, Georgi N. Vayssilov, Notker Rösch
We report the first computational study with a sophisticated quantum mechanics/molecular mechanics (QM/MM) technique that addresses the effect of the aluminum content
on the properties of acidic zeolites. To account for both electrostatic and mechanical interaction
between the QM cluster and its MM environment, we used cluster models embedded in the
covalent variant of the elastic polarizable environment (covEPE) [Nasluzov, V. A.; Ivanova, E.
A.; Shor, A. M.; Vayssilov, G. N.; Birkenheuer, U.; Rösch, N. J. Phys. Chem. B2003, 107,
2228]. For the practical application of the covEPE method, it was necessary to develop a new
force field for Al containing zeolites. Two types of zeolite materials, FAU and MFI, were employed
as examples. We modeled the variation of the Al content both in the MM environment and in
the QM cluster, and we studied pertinent properties of bridging OH groups of the zeolite
frameworks, OH vibrational frequencies, and deprotonation energies. The computational results
suggest that the local structure and the location of the OH groups exert a stronger effect than
the variation of the Al content of the framework.