Frenkel, Frenkel Defect
							Index
		Yakov Ilich Frenkel (1894 to 1952) was a Russian theoretical physicist who worked on the solid and liquid states of matter.   The properties of solids are frequently controlled by the defects they contain, and the "Frenkel pair" is a vacancy- interstitial defect pair that is favored thermo- dynamically in some materials. The diagram illustrates this defect for an ionic solid where the small cation is displaced into an interstitial location creating a cation vacancy. The interstitial cation has a net positive charge and the cation vacancy a net negative charge, the pair being electrically neutral.
					From: Callister,  "Materials Science and Engineering,"  Wiley (1994)
		The diagram shows a Frenkel pair forming a bound system with an electric dipole moment.  In an electric field at a high enough temperature the dipole can reorient and the material can become electrically polarized. If the material is cooled to a low temperature in the applied field it may retain this electrical polarization when the applied field is removed.  At any temperature above 0 K, the dipole has some probability of dissociating into two charged point defects and their motion via field moderated diffusion will contribute to the electrical conductivity of the material. This is known as ionic conductivity.