From AC-STEM Image to 3D Structure: A Systematic Analysis of Au55 nanocluster

Aberration-corrected scanning electron microscopy (AC-STEM) can provide valuable information on the atomic structure of nanoclusters, an essential input for gaining an understanding of their physical and chemical properties. A systematic method is presented here for the extraction of atom coordinate...

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Bibliographic Details
Published inarXiv.org
Main Authors Bersha, Kusse S, Peña-Torres, Alejandro, Jónsson, Hannes
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 10.05.2021
Subjects
Atomic interactions
Atomic structure
Chemical properties
Clusters
Density functional theory
Electron density
Flat surfaces
Icosahedral phase
Mathematical analysis
Nanoclusters
Room temperature
Scanning transmission electron microscopy
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Summary:Aberration-corrected scanning electron microscopy (AC-STEM) can provide valuable information on the atomic structure of nanoclusters, an essential input for gaining an understanding of their physical and chemical properties. A systematic method is presented here for the extraction of atom coordinates from an AC-STEM image in a way that is general enough to be applicable to irregular structures. The two-dimensional information from the image is complemented with an approximate description of the atomic interactions so as to construct a three-dimensional structure and, at a final stage, the structure is refined using electron density functional theory (DFT) calculations. The method is applied to an AC-STEM image of Au55. Analysis of the local structure shows that the cluster is a combination of a part with icosahedral structure elements and a part with local atomic arrangement characteristic of crystal packing, including a segment of a flat surface facet. The energy landscape of the cluster is explored in calculations of minimum energy paths between the optimal fit structure and other candidates generated in the analysis. This reveals low energy barriers for conformational changes, showing that such transitions can occur on laboratory timescale even at room temperature and lead to large changes in the AC-STEM image. The paths furthermore reveal additional cluster configurations, some with lower DFT energy and providing nearly as good fit to the experimental image.
ISSN:2331-8422