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
![](formulas1/image146.gif) |
(13) |
![](formulas1/image148.gif) |
(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
![](formulas1/image157.gif) |
(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
![](formulas1/image159.gif) |
(16) |
|