BAND THEORY OF LINEAR AND NONLINEAR SUSCEPTIBILITIES OF SOME BINARY IONIC INSULATORS

The linear and nonlinear optical responses in a large number of cubic insulators are studied by means of first-principles local-density calc ulations. Complete results on band structures, frequency-dependent die lectric functions, and frequency-dependent third-order nonlinear susce ptibilities chi((3))(omega) (in the simplest form as the third-harmoni c generations) are presented for 27 alkali halides, alkali-earth fluor ides, oxides, and sulfides. They are LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, RI, RbF, RbCl, RbBr, RbI, CaF2, SrF2, CdF2, B aF2, MgO, CaO, SrO, BaO, MgS, CaS, and SrS. The results are compared w ith the existing experimental data and other calculations. The effecti veness of using a ''scissor operator'' to correct the gap underestimat ion in the local-density-approximation theory is assessed. It is shown that the full band-structure approach for the chi((3))(0) calculation in these crystals gives results in very good agreement with experimen tal data, especially in the anisotropic coefficient of the nonvanishin g tenser elements.