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

(13)

(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 

(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

(16)