# Materials 

## Clausius–Mossotti relation

The Clausius–Mossotti relation expresses the dielectric constant (relative permittivity, εr) of a material.

$$\frac {\epsilon _{\mathrm {r} }-1}{\epsilon _{\mathrm {r} }+2}}={\frac {N\alpha }{3\epsilon _{0}}$$

where * $\epsilon_{r}=\epsilon /\epsilon _{0}$ is the dielectric constant of the material * $\epsilon_{0}$ is the permittivity of free space * $N$ is the number density of the molecules (number per cubic meter), and * $\alpha$ is the molecular polarizability in SI-units (C·m2/V).