Molecular dynamics simulation of Coulomb explosion and structural changes in silicon

Strong electronic stopping of high energy ions can lead to Coulomb explosion in which electron stripping causes repulsive interaction among positively charged atoms along ion tracks. Using molecular dynamics simulations and introducing an ionization pulse which lasts for different time periods, Coulomb explosion and structural evolution up to a time scale of 20 ps were modeled in Si. The time periods of ionization pulses play an important role to determine radius of melting/amorphous regions after structural relaxation. For a long ionization, the amorphous/melting region can expand and become larger than the originally ionized region, while the opposite is observed for short ionization. The melting and amorphization occur with a time scale of <1 ps, and are accompanied with shock wave creations.