Simplified predictions of Hamaker constants from Lifshitz theory

Approximations to Lifshitz theory are developed to estimate the van der Waals interaction of coated and uncoated nonmetallic half spaces as a function of separation distance. Using a three-parameter representation of the dielectric spectrum of each material, based only on refractive index data from the visible part of the spectrum and the static dielectric constant, the approximations yield nonretarded Hamaker constants within an average error of 4% of corresponding values computed from rigorous evaluation of Lifshitz theory with the complete dielectric spectra. The effects of retardation and a coating on one of the half-spaces can also be estimated from the approximations but with less accuracy. These approximations should be useful in semiquantitative applications requiring a very large number of such evaluations but not a high level of precision (e.g., to screen materials to be used as a coating or to assess stability to flocculation).