Hamaker constant

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

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

where $\rho _{1}$ and $\rho _{2}$ 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 Hamaker constant provides the means to determine the interaction parameter C from the Van der Waals pair potential, $w(r)=-C/r^{6}$ .

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 $1/r^{6}$ ; this is called the retarded regime, and the result is a Casimir–Polder force.

References

↑ 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
↑ Seung-woo Lee and Wolfgang M. Sigmund. "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. Volume 204, Issues 1-3, 23 May 2002, Pages 43–50.

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Hamaker constant

See also

References