Temperature effects on the impurity segregation in diluted metallic alloys

Abstract

The impurity segregation in diluted transition-metal bimetallic alloys is a subject of study in many fields of interest and still deserves more understanding. Using a tight-binding model for the case of a single substitutional metal impurity the segregation is investigated analysing the segregation energy. Different impurity positions are considered from the (001) top surface to a number of planes below it on a simple cubic lattice. With only one orbital per site, the impurity potentials are determined in order to satisfy charge neutrality through the Friedel sum rule. In particular, our attention will be mainly directed to the substitutional impurity located in the surface and in the bulk. Temperature effects are considered through the Sommerfeld Expansion. Interesting effects on the segregation energy are pointed out such as the appearance of a quantum interference on the electronic states due to the surface itself. The obtained trend of the segregation energy profile is in good agreement with the surface concentration experimental data.