Nonlinear electric properties of alkali metal halides

The first and second hyperpolarizabilities as well as the dipole moments and dipole polarizabilities are studied for a series of the alkali metal halides (MeX, Me = Li, Na, K, X = F, Cl, Br). The static results have been calculated at various levels of including the electron correlation contribution. The frequency-dependent data for different nonlinear optical processes correspond to TDHF calculations and can be approximately scaled for the electron correlation contribution. The present study also gives a systematic comparison of the performance of the so-called Pol basis sets and the recently developed basis sets (HyPol) designed for calculations of electric hyperpolarizabilities. Several regularities in the calculated data are observed and discussed in terms of ionic models supplemented by the electron density confinement effect. For some of the studied systems the first and second hyperpolarizabilities are found to have interestingly high values, comparable to those for molecules used in nonlinear optical materials.