The method of making Carbon nanotubes (CNT) from which various applications are expected is being established. Therefore, it begins to be important to know the behavior of adatoms or ad-molecules inside and outside of the wall of CNT, because it is necessary to aim at the device application in the future. Since we cannot produce a single-type CNT selectively in experiment, theoretical approach for adatom on CNT is necessary to know the property of adatoms on CNT. We calculated adatoms on graphene sheet, using the first-principles calculation as a prototype for CNT. We investigated the binding energy, the stable site and the migration barrier energy for many atomic species. The suitable atomic species can be chosen as each application from those results.
The three atomic species, Mo, Pt and Ag are picked up as an example of metallic atom adsorption on the inside and outside of the wall of the CNT. Mo shows very strong binding with graphene sheet. Ag has very weak binding energiy with graphene sheet. The binding energy for Pt on graphene sheet is not strong and not weak. Moreover, Pt itself is very important for catalysis.
Our calculations are performed based on the density functional theory within the LDA or GGA. We employed 3x3 graphene sheet and CNT of (6,0) and (8,0).
The result for Mo shows us that the adsorption site location depends sensitively on the radius of CNT. In contrast to Mo, the adsorption site of Pt is the bridge site for every CNT we calculated. The difference of adsorption on the inside and outside of CNT is also investigated.
The results will be very important to select suitable materials for covering, nanostructuring and encupsulating with CNT.
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