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Abstract

We present a first-principles density functional theory approach to study the electron-phonon coupling of semiconductor nanoclusters using the self-consistent change of the potential caused by a frozen-phonon distortion of the lattice. This approach has been examined by comparing the results with ab initio linear-response calculation and allows us to study the electron-phonon coupling of nanoclusters with radii up to 16 A (around 1000 atoms) at the level of density functional perturbation theory. We further study the electronic relaxation processes between discrete electronic states of silicon nanoclusters through coupling to the lattice and compare our results with experiments. An increase of electron-phonon coupling strength with decreasing cluster size is obtained from our calculation. We also find that the absorption and emission of vibrons leads to an ultrafast (femtosecond) oscillation in the occupation probability of the excited electronic state given by the electron-phonon coupling. The envelope function of the occupation probability decays exponentially due to the phonon lifetime (around picosecond) and potentially the electron trapping (around picosecond) of surface states.