Bond-orbital theory of linear and nonlinear electronic response in ionic crystals. I. Linear response

Materials characterization for optical device purposes relies heavily on a knowledge of material compliances related to dielectric response. These include both linear response (dielectric constant) and various orders of nonlinear response involving electro-optics (Kerr and Pockels effects, harmonic generation, etc.) and elasto-optics (light scattering, piezoelectrics, etc.) All these properties follow, in principle, from an adequate description of electronic bonding in insulators and semiconductors. This paper sets out a bond-orbital theory of dielectric response which, it is anticipated, will eventually lead to a global semiquantitative representation of all these various properties as functions of such readily available measures as formal valency, bond length, ionic radii, etc. In its initial form, as presented here, it is used to obtain just such an expression for the electronic dielectric constant of pretransition-metal halides and chalcogenides. The root-mean-square accuracy, over 28 halides, is 2.4% and over 44 materials in all, about 3.4%. In the companion paper (II) a similar calculation is carried out for nonlinear response on the same materials.