The dielectric function e which connects the dielectric displacement and the electric field vector is closely related to the susceptibility χ :
.
The frequency dependence of the susceptibility is very characteristic for a material since it incorporates vibrations of the electronic system and the atomic cores as well as contributions from free charge carriers.
The following susceptibility types are supported by SCOUT:
Appropriate models for interband transitions are discussed in the section on KKR dielectric function models.