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.     «

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 an...     »

ISI Document Delivery No.: 504PW Times Cited: 9 Cited Reference Count: 56 Shor, Alexei M. Shor, Elena A. Ivanova Laletina, Svetlana Nasluzov, Vladimir A. Vayssilov, Georgi N. Roesch, Notker Laletina, Svetlana/H-9190-2012 Russian Science Support Foundation; Krasnoyarsk Regional Scientific Foundation [G18017]; Siberian Branch of the Russian Academy of Sciences [79]; National Science Fund and the National Center for Advanced Materials UNION (Bulgaria); Deutsche Forschungsgemeinschaft; Fonds der Chemischen Industrie (Germany) E.A.I.S. is grateful for an individual grant (for the year 2008) from the Russian Science Support Foundation. S.S.L. is thankful for individual support by the Krasnoyarsk Regional Scientific Foundation (Grant No. G18017). This work was supported as an Integration Project of the Siberian Branch of the Russian Academy of Sciences (Grant No. 79) and Project no. 51 of Priority Program No. 27 of the Executive Committee of the Russian Academy of Sciences. We also acknowledge financial support of the National Science Fund and the National Center for Advanced Materials UNION (Bulgaria), Deutsche Forschungsgemeinschaft, and Fonds der Chemischen Industrie (Germany). 9 Elsevier science bv Amsterdam     «

ISI Document Delivery No.: 504PW Times Cited: 9 Cited Reference Count: 56 Shor, Alexei M. Shor, Elena A. Ivanova Laletina, Svetlana Nasluzov, Vladimir A. Vayssilov, Georgi N. Roesch, Notker Laletina, Svetlana/H-9190-2012 Russian Science Support Foundation; Krasnoyarsk Regional Scientific Foundation [G18017]; Siberian Branch of the Russian Academy of Sciences [79]; National Science Fund and the National Center for Advanced Materials UNION (Bulgaria); Deutsche Forschungsgemeinschaft; Fonds de...     »