The Mott criterion describes the critical point of the metal–insulator transition. The criterion is

${\displaystyle n^{-1/3}<Ca_{0}^{*},}$

where ${\displaystyle ~n}$ is the electron density of the material and ${\displaystyle a_{0}^{*))$ the effective bohr radius. The constant ${\displaystyle C}$, according to various estimates, is 2.0, 2.78,4.0, or 4.2.

If the criterion is satisfied (i.e. if the density of electrons is sufficiently high) the material becomes conductive (metal) and otherwise it will be an insulator.^[1]