Ab initio study of transition metals impurities and stability of complexes in germanium (Ge)

Abstract

By means of density functional theory, we present results of an ab initio calculation of vacancy-interstitial complexes (T_Ge -V_nGe I_T , 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 T_Ge -V_nGe I_T for the neutral charge state were obtained. Our results show that under equilibrium conditions, vacancy-interstitial complex T_Ge -V_nGe I_T formed with formation energies not higher than –1.00 eV. The formation energy result showed that the T_Ge -V_nGe I_T 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 T_Ge -V_Ge I_T are stable. For the T_Ge -V_2Ge I_T and T_Ge -V_3Ge I_T , 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