Computational investigation of intrinsic localization in crystalline Si

We investigate numerically existence and dynamical properties of intrinsic localization in crystalline silicon through the use of interatomic Tersoff force fields. We find a band of intrinsic localized modes (discrete breathers) each with lifetime of at least 60 ps in the spectral region 548-578 cm(-1), located just above the zone end phonon frequency calculated at 536 cm(-1). The localized modes extend to more than second neighbors and involve pair central-atom compressions in the range from 6.1% to 8.6% of the covalent bond length per atom. Finite temperature simulations show that they remain robust to room temperatures or higher with a typical lifetime equal to 6 ps.