{"term":{"id":"08856","title":"polarization density","longtitle":"IUPAC Gold Book - polarization density","doi":"10.1351\/goldbook.08856","code":"08856","status":"current","synonym":"<em>synonym<\/em>: dielectric polarization","definitions":[{"id":1,"text":"Change in electric dipole moment per unit volume of dielectric material in response to its exposure to an electric field.","notes":{"1":"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.","2":"Polarization density (unit \\(\\pu{C m-2}\\)) is defined as \\(P = \\varepsilon E - \\varepsilon_{0} E\\), where \\(\\varepsilon E {=D}\\) is so-called electric displacement, \\(E\\) the electric field strength, \\(\\epsilon_{0}\\) the vacuum permittivity and \\(\\varepsilon = \\varepsilon_{\\rm{r}}\\varepsilon_0\\) permittivity of the dielectric material. The ideal dependence of \\(P\\) on \\(E\\) is linear: \\(P = \\varepsilon_{0}\\chi E\\), where \\(\\chi = \\varepsilon_{\\rm{r}} - 1\\) is electric susceptibility. Non-linearity of this dependence gives rise to non-linear optical effects."},"links":[{"term":"dielectric material","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/08790"}],"sources":["PAC, 2022, 94, 15. 'Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)' on page 42 (https:\/\/doi.org\/10.1515\/pac-2020-0501)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/08856\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/08856\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/08856\/plain"},"citation":"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. 10.1351\/goldbook.08856","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-04-18T09:11:09+00:00"}}