Electrodynamic attractive forces

Electrodynamic Attractive Forces and Work of Adhesion Between Cells and Solid Surfaces... 

At a finite distance, where the surface does not come into molecular contact, equilibrium is reached between electrodynamic attractive and electrostatic repulsive forces (secondary minimum). At smaller distance there is a net energy barrier. Once overcome, the combination of strong short-range electrostatic repulsive forces and van der Waals attractive forces leads to a deep primary minimum. Both the height of the barrier and secondary minimum depend on the ionic strength and electrostatic charges. The energy barrier is decreased in the presence of electrolytes (monovalent < divalent [Pg.355]

Dispersion is inherently a quantum-mechanical phenomenon we would need to understand quantum electrodynamics to develop a rigorous model of dispersion. However, it can be viewed classically as follows Nonpolar molecules are really only nonpolar when the electron cloud is averaged over time. In a given snapshot of time, the molecule has a temporary dipole moment. Dispersion forces result from the instantaneous nonsymmetry of the electron cloud surrounding a nucleus. The instantaneous dipole moment induces a dipole in a neighboring molecule, leading to an attractive force. 

The atomic electrons move around the nucleus as a result of the attractive electrostatic Coulomb force between the positive nucleus and the negative charge of the electron. According to classical electrodynamics, the revolving electrons ought to continuously radiate part of their energy, follow a spiral orbit, and eventually be captured by the nucleus. Obviously, this does not happen atoms exist and are stable. 

In DLVO theory van der Waals attraction and electrostatic forces are added. One may question whether this superposition is justified. Could it not be that electrodynamic effects influence the electrostatic force or vice versa and that electric charges change the van der Waals interaction In a strict sense, van der Waals and electrostatic... 

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