Application of classical liquid state methods to the calculation of optical absorption bands in fluids

摘要

Numerical results are presented for a classical model describing optical absorption in a fluid of nonpolar linearly polarizable molecules. The model corresponds to the microscopic Yvonndash;Kirkwood equations with frequencyhyphen;dependent molecular polarizability. The dynamic response of the model system to an externally applied electric field is identical to that predicted by the muchhyphen;studied quantum Drude oscillator model. A fast and reliable numerical method is described, based on that proposed by Gillan for the solution of the Ornsteinndash;Zernike equation of classical liquid state theory, which allows more sophisticated results than those obtained to date. In particular, the evolution of the optical absorption band is studied for hard sphere and Lennardhyphen;Jones fluids, in which the molecular centerhyphen;ofhyphen;mass positions are described by realistic pair distribution functions. Both neat fluids and impurity systems are considered. A number of spectroscopic properties are calculated, including the renormalized dynamic polarizability and the dynamic dielectric constant.