New applications of the equation-of-motion method: Optical properties

Abstract

The equation-of-motion method offers advantages in the calculation of properties of large structural models, of the kind recently developed for a-Si (104 or more atoms). Originally developed for calculating densities of states, it has been shown to be adaptable to a wide variety of other purposes, including the study of localization, conductivity and the Hall effect. Recently we have shown how it may be used to calculate linear optical properties as a function of frequency. Here we present new calculations for a-Si and a-Si:H, using various structural models. The method may be further extended to evaluate nonlinear optical coefficients χ(2)(ω) and χ(3)(ω); we are applying it to the study of χ(3)(ω) for crystalline and amorphous silicon. A conventional approach to this problem, such as calculating eigenstates, would be totally impractical.