Similarly calculated values for carbon tetrachloride and water. Th is is shown in Table 13.1, together with First, for hydrocarbons, treating them asĪn assembly of CH2 groups, we have C z 5 10'8 J m6 and r ¼ 3.3 1028 m# per CH2 Let us consider three cases more specifically. Table 6.1) and of number density r ¼ 3 ġ028 m# (corresponding to atoms of radius ~0.2 nm), the Hamaker constant isĪ ¼ p2 10'7 ð3 1028 Þ2 z 10!9 J ð100 zJ or 10!2 ergÞ: For example, if each body isĬomposed of atoms for which C ¼ 10'7 J m6 (cf. Liquid, are about 10!9 J for interactions in a vacuum. Typical values for the Hamaker constants of condensed phases, whether solid or (1936), did much of the earlier work that advanced understanding of the forces between Some common geometries are shown in Figure 13.1, given in terms of the conventionalĪfter Hamaker (1937), who together with Bradley (1932), Derjaguin (1934), and de Boer This procedure can be carried outįor other geometries as well (cf. Obtain the “two-body” potential for an atom near a surface (Eq. Interatomic van der Waals pair potential of the form w(r) ¼ ,/r6, one may sum (integrate) the energies of all the atoms in one body with all the atoms in the other and thus That the interaction is nonretarded and additive. Starting at the simplest level, we shall assume Let us begin by deriving the van der Waals interaction energies in a vacuumįor pairs of bodies of different geometries. Interactions, they are always present and can be important both at small and large Intermolecular forces, for while they are not as strong as Coulombic or H-bonding Van der Waals Force-Laws for Bodies of DifferentĪs we saw in Part I, van der Waals forces play a central role in all phenomena involving
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