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

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Abstract

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)

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