Surface modes in a semi-infinite slab of finite thickness having the caesium cloride structure

Abstract

We consider the dynamics of a semi-infinite slab having the caesium chloride structure, the free surfaces of which are normal to the (001) surface. The calculations are made using the rigid ion model. Besides the Coulomb interaction, the overlap interaction of the Born-Mayer type between the nearest neighbours is taken into account. Slabs of CsCl of 14, 20 and CsI of 14 ionic layers are considered. The nature and number of surface modes for wave propagation along [10] and [11] directions in CsCl and CsI are discussed. The effect of reducing the charge on the ions on these surface modes is also reported. The i.r. absorption spectrum for the CsCl slab of 14 layers is also presented in this paper.