Chapter 18. Forces of Attraction Between Particles. Particles attract one another because the molecules that constitute them do so. Molecular-pair interactions of the order of magnitude of kT, the thermal energy of a molecule, can be neglected. Dispersion-force interactions, however, are several times kT. Hamaker theory is the molecular approach to this subject, starting with the attraction between molecules and calculating the resulting attraction between particles by summing the attraction between each molecule in one particle with every molecule in the adjoining particle. The summations are approximated by integrations. The alternative molar approach, by Lifshitz, starts with the electric properties of the whole particle and derives attractive potentials therefrom. A reasonable account of heterogeneous attraction through a liquid medium can be made. As well as treatments by theory, attractive forces between some solids have been measured directly.
Key Words: dispersion of light, Hamaker constant, Hamaker theory, heterointeraction,
homointeraction, induced dipole, Jacob’s box, Lennard-Jones potential,
Lifshitz theory, London constant, polarizability
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