Ab initio study of transition metals impurities and stability of complexes in germanium (Ge)
By means of density functional theory, we present results of an ab initio calculation of vacancy-interstitial complexes (TGe -VnGe IT , for n = 1, 2, 3 and T: Cr, Mo, W, Mn and Fe) in Ge. The projector-augmented wave pseudo-potential within the generalized gradient approximation was used for all calculations. Structural properties and formation energies of the TGe -VnGe IT for the neutral charge state were obtained. Our results show that under equilibrium conditions, vacancy-interstitial complex TGe -VnGe IT formed with formation energies not higher than –1.00 eV. The formation energy result showed that the TGe -VnGe IT is energetically more favourable for n = 1 and 2 than n = 3. The stabilities of the vacancy-interstitial complexes were obtained from their binding energies. For all T, the binding energies of the TGe -VGe IT are stable. For the TGe -V2Ge IT and TGe -V3Ge IT , their binding energies lie between 1.79 and 6.10 eV and defect complexes are stable.
Keywords: Density functional theory, vacancy-interstitial, formation energy, impurities