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London-van der Waals Force
London-van der Waals Surface Energy Between Particles
The London-van der Waals surface energy and force between two
spherical particles of diameters
 and
 as show
in Figure 4 was evaluated by Hamaker (1937). The corresponding
surface energy is given as
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(13) |
| where |
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(14) |
is the distance between particles center and s is the separation distance between surfaces.
Figure 4. Schematics of contact of two dissimilar spheres.
For equal size particles,  ,  , and
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(15) |
As noted before, A is typically of the order of 10-19 to 10-21 J and depends
on the properties of particles (of composition 1) and suspending medium
(composition 2). Accordingly, the effective Hamaker constant is given by
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(16) |
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