Term: Drude–Nernst equation (for electrostriction)
https://doi.org/10.1351/goldbook.DT07364

Definition:
Equation describing the contraction (ΔVel) taking place in a dielectric medium of relative static permittivity ɛr (formerly called dielectric constant) upon introduction of an ion of charge number z and radius r: \[\Delta V_{\text{el}} = -\frac{\left ( z\,e \right )^{2}}{2\,r\,\varepsilon_{\text{r}}}\frac{\partial\left ( \text{ln}\varepsilon_{\text{r}}\right)}{\partial\,p}\] with e the elementary charge.

Note: Inasmuch as the derivative of lnɛr with respect to pressure, ∂(lnɛr)/∂p, is not known for all media, there are approximations to evaluate this term as a function of ɛr and of the isothermal compressibility of the medium, κ T.

Related Terms:
1) permittivity (http://doi.org/10.1351/goldbook.P04507).
2) dielectric constant (http://doi.org/10.1351/goldbook.D01697).
3) charge number (http://doi.org/10.1351/goldbook.C00993).
4) elementary charge (http://doi.org/10.1351/goldbook.E02032).

Source: PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 327 (https://doi.org/10.1351/pac200779030293)

Citation: 'Drude–Nernst equation (for electrostriction)' 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.DT07364

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