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Theoretical Explanation of Pt Trimers Observed by Z-Contrast STEM

Published online by Cambridge University Press:  10 February 2011

Karl Sohlberg ,
Sokrates T. Pantelides  and
Stephen J. Pennycook
Karl Sohlberg
Affiliation:
Solid State Division, P.O. Box 2008, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6031
Sokrates T. Pantelides
Affiliation:
also, Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235
Stephen J. Pennycook
Affiliation:
also, Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235
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Abstract

First-principles quantum-mechanical calculations on γ-alumina have revealed a fascinating “reactive sponge” phenomenon. γ-alumina can store and release water, but in a unique, “reactive” way. This “reactive sponge process” facilitates the creation of aluminum and oxygen vacancies in the alumina surface. Earlier atomic-resolution Z-contrast STEM images of ultradispersed Pt atoms on a γ-alumina support showed the individual atoms to form dimers and trimers with preferred spacings and orientations that are apparently dictated by the underlying support[1]. In turn, the reactive sponge property of γ-alumina is the key to understanding the Pt clusters. Our calculations demonstrate that if three Pt atoms fill three vacancies created during the reactive sponge process, the resulting geometry precisely matches that of the Pt trimers observed in the Z-STEM images. Understanding the initial nucleation of small clusters on the complex gamma alumina surface is an essential first step in determining the origins of catalytic activity.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 589 , 1999 , 241
Copyright
Copyright © Materials Research Society 2001

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