Hamaker-Konstante

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 of atoms per unit volume in two interacting bodies and C is the coefficient in the particle-particle pair interaction.

The Hamaker constant provides the means to determine the interaction parameter C from the van der Waals (vdW) 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.

See also

• Hamaker theory
• van der Waals Forces
• Intermolecular forces