Hamaker functions for kaolinite and montmorillonite

An oscillator representation for the calculation of van der Waals forces/energies is presented for kaolinite and montmorillonite. The non-retarded Hamaker constants across water (air) are 5.1 (59.2) zJ and 7.3 (75.4) zJ for montmorillonite and kaolinite, respectively. The combined effect of retardation and geometrical peculiarities of the monmorillonite system are discussed briefly. It is shown that the van der Waals free energy between two montmorillonite layers of finite thickness, immersed in water, changes from attractive to repulsive at a separation distance primarily determined by their thickness.