London-van der Waals Force
van der Waals Force Near a Surface
The van der Waals for a sphere near a surface as shown in Figure 1 is given by
, |
(4) |
where is the Hamaker
constant for substances 1 and 2 in presence of medium 3,
and is separation
distance. For a particle attached to a wall,
is
about 4 to 10 .
Typically is used.
Figure 1. Schematics of a particle near a wall.
For cylinder-planar surface contacts shown in Figure 2,
, |
(5) |
![](formulas1/image114.gif)
Figure 2. Schematics of a cylindrical particle near a wall.
For two planar surfaces shown in Figure 3,
, |
(6) |
z0
Figure 3. Schematics of a two planar surface at a separation distance of z0. |