Hamaker constant

Hamaker constant

The Hamaker constant A can be defined for a van der Waals (vdW) body-body interaction::A=pi^2 imes C imes ho_1 imes ho_2where ho_1 and ho_2 are the number of atoms per unit volume in two interacting bodies and C is the coefficient in the particle-particle pair interaction. [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 ]

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.

ee also

*Hamaker theory
*van der Waals Forces
*Intermolecular forces

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Dilatant — A dilatant (also termed shear thickening) material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the acronym STF, is an example of a non Newtonian fluid. Comparison of the behavior …   Wikipedia

  • DLVO theory — The DLVO theory is named after Derjaguin and Landau, Verwey and Overbeek. The theory describes the force between charged surfaces interacting through a liquid medium. It combines the effects of the van der Waals attraction and the electrostatic… …   Wikipedia

  • Force field (chemistry) — In the context of molecular mechanics, a force field (also called a forcefield) refers to the functional form and parameter sets used to describe the potential energy of a system of particles (typically but not necessarily atoms). Force field… …   Wikipedia

  • Casimir effect — Casimir forces on parallel plates Casimir forces on parallel pl …   Wikipedia

  • Fused quartz — A sphere manufactured by NASA out of fused quartz for use in a gyroscope in the Gravity Probe B experiment. It is one of the most accurate spheres ever created by humans, differing in shape from a perfect sphere by no more than 40 atoms of… …   Wikipedia

  • Van der Waals force — In physical chemistry, the van der Waals force (or van der Waals interaction), named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule)… …   Wikipedia

  • Champ de force (chimie) — Pour les articles homonymes, voir champ de force. Un champ de force peut par exemple être utilisé afin de minimiser l énergie d étirement de cette molécule d éthane. Dans le cadre de la m …   Wikipédia en Français

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”