Сибирский федеральный университет

Тип публикации: статья из журнала

Год издания: 2009

Идентификатор DOI: 10.1016/j.chemphys.2009.07.006

Ключевые слова: Density functional calculations, Embedded cluster approach, Convergence study, Adsorption complexes in zeolites, QM/MM

Аннотация: Recently we presented an improved scheme for constructing the border region within the covEPE hybrid quantum mechanics/molecular mechanics (QM/MM) embedded cluster approach for zeolites and covalent oxides in the framework of the elastic polarizable environment method. In the present study we explored how size and shape of the embedded QM cluster affect the results for structural features, energies, and characteristic vibrational frequencies of two model systems, adsorption complexes of H(2)O and Rh(6) in faujasite frameworks that contain Bronsted acid sites. Comparison of calculated characteristics of different QM cluster models suggests that the local structure and vibrational frequencies of acid sites in adsorbate-free zeolite are well reproduced with all embedded QM clusters, which contain from 5T to 14T atoms. A proper description of systems with an H(2)O adsorbate requires larger QM clusters, with at least 8T atoms, whereas vibrational frequencies of OH groups participating in hydrogen bonds demand even larger quantum clusters, preferably with 12T or 14T atoms. The structure of the metal particle in adsorbed rhodium species is well reproduced with all QM clusters scrutinized, from 12T atoms. Larger QM models, with 18T or 24T atoms, are recommended when one aims at a high accuracy of Rh-O and Rh-H distances and characteristic energies. (C) 2009 Elsevier B.V. All rights reserved.

Журнал: CHEMICAL PHYSICS

Выпуск журнала: Vol. 363, Is. 1-3

Номера страниц: 33-41

ISSN журнала: 03010104

Место издания: AMSTERDAM

Издатель: ELSEVIER SCIENCE BV

• Shor A.M. (Institute of Chemistry and Chemical Technology,Russian Academy of Sciences)
• Shor E.A.I. (Siberian Federal University)
• Laletina S. (Institute of Chemistry and Chemical Technology,Russian Academy of Sciences)
• Nasluzov V.A. (Siberian Federal University)
• Vayssilov G.N. (Faculty of Chemistry,University of Sofia)
• Rosch N. (Technische Universitat Munchen,Department Chemie,Catalysis Research Center)

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