Hamaker Constant
Encyclopedia
The Hamaker constant A can be defined for a Van der Waals (VdW) body-body interaction:
where
and 
are the number of atom
s 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 pair potential,
.
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
; this is called the retarded
regime and the result is a Casimir–Polder force.
where
and are the number of atomAtom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s 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 pair potential,
.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
; this is called the retardedRetarded potential
The retarded potential formulae describe the scalar or vector potential for electromagnetic fields of a time-varying current or charge distribution. The retardation of the influence connecting cause and effect is thereby essential; e.g...
regime and the result is a Casimir–Polder force.