Effective medium approximations

In materials science, effective medium approximations (EMA) or effective medium theory (EMT) pertain to analytical or theoretical modeling that describes the macroscopic properties of composite materials. EMAs or EMTs are developed from averaging the multiple values of the constituents that directly make up the composite material. At the constituent level, the values of the materials vary and are inhomogeneous. Precise calculation of the many constituent values is nearly impossible. However, theories have been developed that can produce acceptable approximations which in turn describe useful parameters including the effective permittivity and permeability of the materials as a whole. In this sense, effective medium approximations are descriptions of a medium (composite material) based on the properties and the relative fractions of its components and are derived from calculations,[1][2] and effective medium theory.[3] There are two widely used formulae.[4]

Effective permittivity and permeability are averaged dielectric and magnetic characteristics of a microinhomogeneous medium. They both were derived in quasi-static approximation when the electric field inside a mixture particle may be considered as homogeneous. So, these formulae can not describe the particle size effect. Many attempts were undertaken to improve these formulae.

  1. ^ Wenshan, Cai; Shalaev, Vladimir (November 2009). Optical Metamaterials: Fundamentals and Applications. Springer. pp. Chapter 2.4. ISBN 978-1-4419-1150-6.
  2. ^ Wang, M; Pan, N (2008). "Predictions of effective physical properties of complex multiphase materials" (Free PDF download). Materials Science and Engineering: R: Reports. 63: 1–30. doi:10.1016/j.mser.2008.07.001.
  3. ^ T.C. Choy, "Effective Medium Theory", Oxford University Press, (2016) 241 p.
  4. ^ M. Scheller, C. Jansen, M. Koch, "Applications of Effective Medium Theories in the Terahertz Regime" in Recent Optical and Photonic Technologies, ed. by K.Y. Kim, Intech, Croatia, Vukovar (2010), p. 231.