Dynamics of a finite harmonic oscillator chain with a surface impurity

Abstract

A method is presented for constructing the normal modes and spectrum of a finite harmonic oscillator chain to which a polyatomic surface impurity is attached. This scheme is a generalization of an earlier theory due to Puszkarski. Special attention is devoted to localized surface modes and to the identification of the circumstances which cause them to occur. Diagnostic calculations have been performed in order to learn how an adsorbed diatomic molecule alters the normal modes and eigenfrequencies of the lattice. Examples are provided of cases where these effects are slight and of others where the perturbation generates localized optical and/or acoustic surface modes.