Classical molecular dynamics simulations were used to study the configurational and energetic properties of the Si self-interstitial. It was shown that the Si self-interstitial could appear in 4 different configurations, characterized by different energetics. Along with the already known tetrahedral, dumb-bell, and extended configurations, a highly asymmetrical configuration was found which had not previously been reported. Using a data analysis technique based upon time averages, the formation enthalpies and the probability of finding the interstitial in a given configuration, both depending upon temperature, were extracted. By the use of thermodynamic integration techniques, the Gibbs free energy and entropy of formation, and the relative concentration of each interstitial configuration as a function of temperature were determined. It was demonstrated that the change of interstitial configuration was correlated with the diffusion process, and 2 different mechanisms for interstitial-mediated self-diffusion were identified. In spite of the microscopic complexity of the interstitial-mediated diffusion process, the results predicted a pure Arrhenius behavior with an activation energy of 4.60eV at 900 to 1685K, in good agreement with experiment. This energy was decomposed in an effective interstitial formation enthalpy of 3.83eV and a migration barrier of 0.77eV, which macroscopically represented the averaged behavior of the different interstitial configurations.

Molecular Dynamics Study of the Configurational and Energetic Properties of the Silicon Self-Interstitial. L.A.Marqués, L.Pelaz, P.Castrillo, J.Barbolla: Physical Review B, 2005, 71[8], 085204