Английская Википедия:Hamaker constant

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In molecular physics, the Hamaker constant (denoted Шаблон:Mvar; named for H. C. Hamaker) is a physical constant that can be defined for a van der Waals (vdW) body–body interaction:

<math>A=\pi^2C\rho_1\rho_2,</math>

where Шаблон:Math are the number densities of the two interacting kinds of particles, and Шаблон:Mvar is the London coefficient in the particle–particle pair interaction. The magnitude of this constant reflects the strength of the vdW-force between two particles, or between a particle and a substrate.

The Hamaker constant provides the means to determine the interaction parameter Шаблон:Mvar from the vdW-pair potential,

<math>w(r) = \frac{-C}{r^6}.</math>

Hamaker's method and the associated Hamaker constant ignores the influence of an intervening medium between the two particles of interaction. In 1956 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 <math>1/r^6;</math> 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

Шаблон:Molecular-physics-stub