IUPAC - polarization density (08856)

polarization density

symbol:

P

, unit:

C m^{- 2}

synonym: dielectric polarization

https://doi.org/10.1351/goldbook.08856

Change in electric dipole moment per unit volume of dielectric material in response to its exposure to an electric field.

Notes:

The electric field causes limited reversible displacements of charged particles that cannot move freely in the dielectric material. Electronic polarization (displacements of electrons) takes a femtosecond. So it is in phase with an alternating electric field, such as that of light. Ionic polarization (of ions in ionic crystals) is also instantaneous. However orientation polarization based on reorientation of permanent dipoles is significantly slower (delayed) and thus often out of phase with the light field.
Polarization density (unit $C m^{- 2}$ ) is defined as $P = ε E - ε_{0} E$ , where $ε E = D$ is so-called electric displacement, $E$ the electric field strength, $ϵ_{0}$ the vacuum permittivity and $ε = ε_{r} ε_{0}$ permittivity of the dielectric material. The ideal dependence of $P$ on $E$ is linear: $P = ε_{0} χ E$ , where $χ = ε_{r} - 1$ is electric susceptibility. Non-linearity of this dependence gives rise to non-linear optical effects.

Source:
PAC, 2022, 94, 15. (Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)) on page 42 [Terms] [Paper]

Citation: 'polarization density' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08856 RIS BibTex EndNote

Div. IV Text XML JSON

Alphabetical Index

Additional Indexes

Version 3.0.1 (7517 Terms)

polarization density