Cluster and periodic density functional study of auger electron emission from conducting carbon nanotubes

Auger core-valence–valence transitions from Carbon nanotubes are investigated using density functionaltheory combined with two different crystal models, namely all-electron molecular cluster andperiodic pseudo-potential. Particular attention is paid to the high emission energy and the highbinding energy features of the spectra: the former are due to the many-body shake-up of Fermielectrons, whereas the latter are related to final-state hole–hole correlations in the valence bands.The calculated spectra, whose width are adjusted to match the experimental valence energy rangeof large-size/infinite nanotubes, show similar peak positions and profiles, although remarkable differencesare detected in the high-binding energy peak due to transitions involving the s-part of thevalence electronic structure. Other components, originating from sp and pp transitions, are foundin excellent agreement with measurements of Auger electrons ejected from bundles of single wallCarbon nanotubes. The high-binding energy mismatch of the two models is essential in interpretingthe quasi-resonance observed at ∼240 eV in most experiments performed on both Graphite andnanotube bundles.