IMPROVED PARAMETRIC REPRESENTATION OF WATER DIELECTRIC DATA FOR LIFSHITZ THEORY CALCULATIONS

Calculations of van der Waals interactions using Lifshitz theory requi re the availability and convenient mathematical representation of diel ectric data for the materials involved, especially in the ultraviolet region of the spectrum, The UV representation of water is especially f requently needed in Lifshitz theory calculations in view of the ubiqui tous appearance of aqueous media in the intervening space between soli d surfaces, both macroscopic and colloidal. We present here a modified parameter set to describe the UV dielectric behavior of water, It fit s the original reflectivity data much more closely than the set usuall y used, and leads to significant changes in calculated Hamaker constan ts-for materials interacting across water, a reduction of as much as 4 0% is seen. These results illustrate the importance of accurate spectr al information, or conversely, the potential uncertainties in calculat ed properties in the absence of extensive and accurate data. (C) 1996 Academic Press, Inc.