Ab initioand empirical-potential studies of defect properties in3C−SiC

Abstract

Density functional theory (DFT) is used to study the formation and properties of native defects in $3C\ensuremath{-}\mathrm{SiC}.$ Extensive calculations have been carried out to determine the formation of point defects and the stability of self-interstitials. Although there is good agreement in the formation of vacancies and antisite defects between the present study and previous calculations, a large disparity appears in the formation of self-interstitials. The most favorable configurations for C interstitials are 〈100〉 and 〈110〉 dumbbells, with formation energies from 3.16 to 3.59 eV, and the most favorable Si interstitial is Si tetrahedral surrounded by four C atoms, with a formation energy of 6.17 eV. The present DFT results are also compared with those calculated by molecular dynamics (MD) simulations using the Tersoff potentials, with parameters obtained from the literature. The formation energies of vacancies and antisite defects obtained by MD calculations are in good agreement with those obtained by DFT calculations. However, the MD calculations yield different results for interstitials energies and structures that depend on the cutoff distances used in the Tersoff potentials. The results provide guidelines for evaluating the quality and fit of empirical potentials for large-scale simulations of irradiation damage and defect migration processes in SiC.