Physical cluster theory of point defect interactions. II. Application to AgCl doped with CdCl2

摘要

The Lidiardhyphen;Teltow approximation (L) describes a point defect system of cation vacancies and divalent impurity cations in AgCl doped with CdCl2as a collection of nearesthyphen;neighbor impurityhyphen;vacancy pairs and unpaired impurities and vacancies. The concentrations of the latter and related by a law of mass action using Debyehyphen;Huuml;ckel activity coefficients for unpaired species. The formalism of the previous paper is applied to the same equilibrium. The leading terms of the exact cluster expansions for activity coefficients in the mass action law are reduced analytically and calculated numerically in two approximations,PandT. The approximationsL, P, andTagree well for concentrations at which an extension ofLindicates that larger defect clusters (triplets, etc.) can be neglected but they tend to diverge at higher concentrations than this, i.e., at impurity contents larger than 7 times; 10minus;3for temperatures greater than or equal to 250deg;C but at lower concentrations for lower temperatures. The agreement betweenPandTapproximations confirms the adequate convergence of the new cluster expansions; the agreement of theLapproximation with them indicates that it is an accurate approximation although it neglects the effects of paired defects and the discreteness of the lattice on the Debyehyphen;Huuml;ckel shielding as well as certain other Coulombic interactions retained inPandT.