Editing Quantum tunnelling (section)

==== Conductivity of crystalline solids ====
While the [[Drude-Lorentz model]] of [[electrical conductivity]] makes excellent predictions about the nature of electrons conducting in metals, it can be furthered by using quantum tunnelling to explain the nature of the electron's collisions.<ref name="Taylor" /> When a free electron wave packet encounters a long array of uniformly spaced [[potential barrier|barriers]], the reflected part of the wave packet interferes uniformly with the transmitted one between all barriers so that 100% transmission becomes possible. The theory predicts that if positively charged nuclei form a perfectly rectangular array, electrons will tunnel through the metal as free electrons, leading to extremely high [[Electrical conductance|conductance]], and that impurities in the metal will disrupt it.<ref name="Taylor" />