Energy landscape of silicon tetra-interstitials using an optimized classical potential
Y. Du, T. J. Lenosky, R. G. Hennig, S. Goedecker, J. W. Wilkins.
Physica Status Solidi B, 248, 2050–2055, (2011)
Mobile single interstitials can grow into extended interstitial defect structures during thermal anneals following ion implantation. The silicon tetra-interstitials present an important intermediate structure that can either provide a chain-like nucleation site for extended structures or form a highly stable compact interstitial cluster preventing further growth. In this paper, dimer searches using the tight-binding (TB) model by Lenosky et al. and density functional calculations show that the compact ground-state Iα 4 and the I4-chain are surrounded by high-lying neighboring local minima. To furthermore explore the phase space of tetra-interstitial structures an empirical potential is optimized to a database of silicon defect structures. The minima hopping method combined with this potential extensively searches the energy landscape of tetra-interstitials and discovers several new low-energy I4 structures. The second lowest-energy I4 structure turns out to be a distorted ground-state tri-interstitial bound with a single interstitial, which confirms that the ground-state tri-interstitial may serve as a nucleation center for the extended defects in silicon.
Keyword(s): Defects;embedded atom model; interatomic potentials; interstitials; ion implantation; silicon