DFT study of the effect of hydrostatic pressure on formation and migration enthalpies of intrinsic point defects in single crystal Si



The dependence of the formation enthalpy (Hf) of the self-interstitial I and the vacancy V on the hydrostatic pressure P was obtained by calculating the formation energy (Ef) and the relaxation volume (vf). The dependence of the migration enthalpy (Hm) of I and V on the pressure P was also obtained by calculating the change of Hf during the migration. Density functional theory calculations were used with 216-atom supercells and with special attention for the convergence of the calculations. The neutral I and V are found to have quasi constant formation energies EfI and EfV for pressures between – 1 GPa to 1 GPa. For the relaxation volume, vfI is almost constant while vfV decreases with increasing pressure P. The formation and migration enthalpies HfI and HmI, respectively, at the [110] dumbbell site are given by HfI = 3.425 – 0.055×P (eV) and HmI = 0.981 – 0.039×P (eV) with hydrostatic pressure P given in GPa. The HfV and HmV dependencies on P are given by HfV =3.543 – 0.024×P2– 0.009×P (eV) and HmV = 0.249 + 0.005×P2 – 0.030×P (eV). These results indicate that hydrostatic pressure leads to a slight increase of the equilibrium concentration and diffusion of vacancies but this increase is considerably smaller than that of self-interstitials (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)