Hamaker constant

The Hamaker constant A can be defined for a Van der Waals (VdW) body–body interaction:

${\displaystyle A=\pi ^{2}\times C\times \rho _{1}\times \rho _{2},}$

where ${\displaystyle \rho _{1}}$ and ${\displaystyle \rho _{2}}$ are the number densities of the two interacting kinds of particles, and C is the coefficient in the particle–particle pair interaction.[1][2] It is named after H. C. Hamaker. The magnitude of this constant reflects the strength of the vdW force between two particles, or between a particle and a substrate.[1]

The Hamaker constant provides the means to determine the interaction parameter C from the Van der Waals pair potential, ${\displaystyle w(r)=-C/r^{6}}$.

Hamaker's method and the associated Hamaker constant ignores the influence of an intervening medium between the two particles of interaction. In the 1950s Lifshitz developed a description of the VdW energy but with consideration of the dielectric properties of this intervening medium (often a continuous phase).

The Van der Waals forces are effective only up to several hundred angstroms. When the interactions are too far apart, the dispersion potential decays faster than ${\displaystyle 1/r^{6}}$; this is called the retarded regime, and the result is a Casimir–Polder force.

See also

• Hamaker theory
• Intermolecular forces
• van der Waals Forces

References

1. Hamaker, H. C. (1937). "The London – van der Waals attraction between spherical particles". Physica. 4 (10): 1058–1072. doi:10.1016/S0031-8914(37)80203-7.
2. Seung-woo Lee and Wolfgang M. Sigmund (23 May 2002). "AFM study of repulsive Van der Waals forces between Teflon AF thin film and silica or alumina". Colloids and Surfaces A: Physicochemical and Engineering Aspects. 204 (1–3): 43-50. doi:10.1016/S0927-7757(01)01118-9.