Auger core-valence–valence transitions from single wall Carbon nanotubes are studied using ab initio atomistic methods, in which a cluster of Carbon atoms is initially located at the equilib- rium positions of a finite-length (6, 6)-tube. Density functional computations, including geometry and restricted Hartree-Fock optimizations, are carried out with the 3–21 G basis set and the exchange and correlation functional by Pedrew-Burke-Ernzerhof. The density of one-electron eigenvalues, entering the optimized ground state of the cluster, is found in excellent agreement with the density of states of infinite nanotubes, as calculated by tight-binding periodic methods. The corresponding orbitals are plugged into the Fermi’s golden rule to determine the first-order spectrum of emitted electrons from the same atomic-site of the core–hole. Finite lifetime effects, in the initial and final states, as well as the electron–phonon interaction, are effectively modeled with a Gauss-Lorentz distribution. Particular attention is paid to final-state, shake-up processes at the Fermi level that are quantitatively included into an asymmetric broadening function. Also considered is the hole–hole coupling in the occupied portion of the valence band, which is treated by the Cini-Sawatzky dis- tortion function. The width of the calculated spectra is adjusted to match the experimental valence energy range of large-size/infinite nanotubes. The theoretical results show similar trends with mea- surements of Auger electrons ejected from bundles of single wall Carbon nanotubes.
Auger core-valence-valence transitions from single wall Carbon nanotubes are studied using ab initio atomistic methods, in which a cluster of Carbon atoms is initially located at the equilibrium positions of a finite-length (6, 6)-tube. Density functional computations, including geometry and restricted Hartree-Fock optimizations, are carried out with the 3-21 G basis set and the exchange and correlation functional by Pedrew-Burke-Ernzerhof. The density of one-electron eigenvalues, entering the optimized ground state of the cluster, is found in excellent agreement with the density of states of infinite nanotubes, as calculated by tight-binding periodic methods. The corresponding orbitals are plugged into the Fermi's golden rule to determine the first-order spectrum of emitted electrons from the same atomic-site of the core-hole. Finite lifetime effects, in the initial and final states, as well as the electron-phonon interaction, are effectively modeled with a Gauss-Lorentz distribution. Particular attention is paid to final-state, shake-up processes at the Fermi level that are quantitatively included into an asymmetric broadening function. Also considered is the hole-hole coupling in the occupied portion of the valence band, which is treated by the Cini-Sawatzky distortion function. The width of the calculated spectra is adjusted to match the experimental valence energy range of large-size/infinite nanotubes. The theoretical results show similar trends with measurements of Auger electrons ejected from bundles of single wall Carbon nanotubes.
Many-Body Effects in Auger Electron Emission from Finite-Length Carbon Nanotubes
SINDONA, Antonio;Pisarra M;RICCARDI, Pierfrancesco;
2011-01-01
Abstract
Auger core-valence–valence transitions from single wall Carbon nanotubes are studied using ab initio atomistic methods, in which a cluster of Carbon atoms is initially located at the equilib- rium positions of a finite-length (6, 6)-tube. Density functional computations, including geometry and restricted Hartree-Fock optimizations, are carried out with the 3–21 G basis set and the exchange and correlation functional by Pedrew-Burke-Ernzerhof. The density of one-electron eigenvalues, entering the optimized ground state of the cluster, is found in excellent agreement with the density of states of infinite nanotubes, as calculated by tight-binding periodic methods. The corresponding orbitals are plugged into the Fermi’s golden rule to determine the first-order spectrum of emitted electrons from the same atomic-site of the core–hole. Finite lifetime effects, in the initial and final states, as well as the electron–phonon interaction, are effectively modeled with a Gauss-Lorentz distribution. Particular attention is paid to final-state, shake-up processes at the Fermi level that are quantitatively included into an asymmetric broadening function. Also considered is the hole–hole coupling in the occupied portion of the valence band, which is treated by the Cini-Sawatzky dis- tortion function. The width of the calculated spectra is adjusted to match the experimental valence energy range of large-size/infinite nanotubes. The theoretical results show similar trends with mea- surements of Auger electrons ejected from bundles of single wall Carbon nanotubes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
