Hamaker constant

The Hamaker constant A is a size for the force between two particles, which act between Van -der- Waals forces. The Hamaker constant is named after the Dutch physicist Christiaan Hamaker Hugo ( 1905-1993 ).

Definition

It is defined by:

Here, they stand for the number of atoms per unit volume in two interacting bodies. C is a parameter for the particle-particle interaction. The SI unit of Hamaker constants is the joule. The values ​​of the constants are extremely small and are in the range of 10-19 to 10-20 joules. The value can be determined by the dielectric constant or the ionization potential.

The Hamaker constant allows the interaction coefficient C from the van der Waals interaction potential to determine:

For example, for the description of the dispersions of the Hamaker constant is important. Decreases its value, this leads to a decrease of the van der Waals interaction energy, which in turn leads to a relative increase of the repulsive interaction between the particles in the suspension, whereby the system becomes more stable. The constant itself may be affected by the solvent used. The attraction potential is also dependent on the material.

The Hamaker constant method and the same negligible matrix effects between the interacting particles. In the 1950s, Yevgeny Lifshitz developed a descriptive model of the van der Waals energy, which takes into account the interaction of the dielectric matrix. It is a description of the macroscopic optical characteristics of the interacting bodies.

The van der Waals forces have a short range of a few hundred angstroms. The Van der Waals interaction potential decreases by a factor, that is, with the sixth power of the distance decreases.