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(a) STEM image of CNT in a region free of zirconia particles. The bright spot enclosed by the CNT is a catalyst particle composed of iron. The top finger structure are MWNTs with 10–20 layers. Across the dashed line we obtain the EELS on transmission shown in part (b). The beam is wide and a spectrum is measured every . The vertical dashed-red lines show transitions corresponding to the elements that are expected to be present in the sample. Neither iron or oxygen are present. Notice, however, the large Zr content. (c) distribution profile on the tube, along the same dashed line in panel (a).
Geometries for different coverage ratios. Below each configuration, the total energy difference with respect the ground state for each coverage is given in eV. Carbon atoms are small-dark circles and zirconium ones are large light. The results for the cell are not shown because the same total energy differences are obtained for .
Charge transfer vs coverage ratio. All coverage ratios are for hollow positions except the point with a coverage ratio of 37.5%, which is a mixed hollow/top configuration.
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