On Hamaker constants: A comparison between Hamaker constants and Lifshitz-van der Waals constants

A review is given of equations from which Hamaker constants can be calculated theoretically for condensed bodies at short distances. Numerical examples obtained from these equations plus Hamaker constants as obtained from colloid chemistry are compared to the Lifshitz-van der Waals constants obtained from the optical properties of condensed bodles over a frequency range from visible light to the X-ray region. The latter constant is regarded as the more correct since only minor assumptions have been made in its derivation. It is shown that the various approximations lead to a large scatter in Hamaker constants. Only for a few expressions are data obtained that agree reasonably well with the Lifshitz-van der Waals constant of the same material. For those materials where no complete absorption spectra are available, these approximated expressions can be used for calculation of their Hamaker constant to a first approximation. Further, a new approximation for the calculation of Hamaker constants for polymers has been introduced. The influence of a third medium on the interaction between two materials is discussed and the occurrence of negative Hamaker constants for the interaction between three different materials is demonstrated.