Authors: B.P. Uberuaga, G. Henkelman, H. Jonsson, S.T. Dunham and W. Windl
Affilation: Los Alamos National Lab, United States
Pages: 104 - 107
Keywords: self-diffusion, clustering, density functional theory, dimer method, BSLYP functional
Density functional theory studies of two systems have been conducted: mechanisms of self-diffusion in Ge and clustering of B in Si. In the case of self-diffusion of Ge, we find for the vacancy mechanism within harmonic transition state theory a diffusion prefactor, which agrees well with experiment but the activation energy is under-estimated by nearly 1 eV when the PW91 functional is used. We propose a cluster correction procedure involving the hybrid B3LYP functional, which brings the activation energy to 3.2 eV, agreeing with experiment. The interstitial and exchange mechanisms contribute negligibly. The reaction pathway of B cluster formation in Si has been studied, with the cluster B3I2 being identified as an intermediary in the formation of B3I-, a dominant cluster. The dimmer method is found to be effective for finding transition states for complex systems. All of the steps identified to date have been shown to be diffusion limited.