STACKING DEFECT AND ELECTRONIC STRUCTURE OF ALLOYS
We have used the Tight-Binding formalism, within the continued fraction technique, in order to study the stacking defect fcc vs hc as a function of electronic filling in the aim to make a general study concerning transition metals of the end of series (like Ir, Pt and Au). With this study we have demonstrated the importance of spd hybridization which affects the d band not only for very low and very high fillings (band borders) but also on all the energy range and therefore all the electronic filling range[21, 22]. We have further applied the same method to mixed systems of transition metals considering in particular CoAu. Applying this method to alloys required to determine first a rule of charge distribution as a function of concentration. Based on DFT calculations we have shown that this rule reduced to a local neutrality rule, per site, species and orbital. Applying this rule in self- consistent TB calculations, we were able to study in a first application, the d level shifts, as a function of concentration in an alloy, which can be associated to core level shifts measured in XPS experiments.
References : ”Role of spd hybridization in the formation of stacking defects at metal surfaces”, A. Jaafar, C. Goyhenex and G. Tréglia, Surf. Sci. 602, 2681 (2008).  ”Formation of stacking defects at surfaces : From atomistic simulations to density functional theory calculations”, A. Jaafar and C. Goyhenex, Solid State Sciences 12, 172 (2010).  ”Rules for Tight-Binding calculations in bi-metallic compounds base- donDensity Functional Theory : the Co-Au case”, A. Jaafar, C. Goyhenex and G. Tr´eglia, J. Phys. Cond. Matter, in press.