Formation of two-impurity complex in dilute alloys observed through perturbed angular correlations of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi></mml:math>rays

Abstract

Interaction between two soluble impurities in metal hosts leads to a nonrandom distribution of the impurity atoms among the lattice sites. The number of the nearest-neighbor impurity-impurity pairs is discussed. It is shown how both the binding energy and the entropy of formation can be extracted for two-impurity complex from the number of these complexes measured as a function of temperature. The method is illustrated by the perturbed-angular-correlation experiment with $^{111}\mathrm{In}$ in dilute alloys of Cu, Ag, and Au with Pt impurity. The entropy of formation found for the In-Pt pair in Cu, Ag, and Au hosts agrees very well with the number of ways in which the pair can be formed in the fcc lattice. The In and Pt impurities are bound, with the binding energy depending significantly on the host.