THEORETICAl STUDY OF IMPERFECTIONs IN IONIC CRYSTAlS

Abstract

In this chapter the relative stabilities of Z 1 center orientations (linear and non linear) at the surfaces ofBe2+, Mg2+ and Ca2+ doped LiCl, NaCl and KCl ionic insulators are examined, in addition to the effects of Z 1 center on the adsorption of atomic halogens (F, Cl, Br, I and At). The clusters are embedded in point ions terminated by partial ionic charges that make to coulomb potentials at the central surface sites approximately equal to the madelung fields ofthe host surfaces. The dependence ofthe relative stabilities of the considered Z 1 orientations on the cationic species is examined. The relation between the electronegativity of the adsorbate and the strength of the adsorbate- substrate interactions is investigated in addition.fto the role of spin pairing.