## Drude–Nernst equation (for electrostriction)

https://doi.org/10.1351/goldbook.DT07364
Equation describing the contraction ($$\Delta V_{\text{el}}$$) taking place in a dielectric medium of relative static @P04507@ $$\varepsilon_{\text{r}}$$ (formerly called @D01697@) upon introduction of an ion of @C00993@ $$z$$ 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 @E02032@.
Note:
Inasmuch as the derivative of $$\text{ln}\varepsilon_{\text{r}}$$ with respect to pressure, $$\frac{\partial (\text{ln}\varepsilon _{\text{r}})}{\partial p}$$, is not known for all media, there are approximations to evaluate this term as a function of $$\varepsilon_{\text{r}}$$ and of the isothermal compressibility of the medium, $$\kappa_{T}$$.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 327 [Terms] [Paper]