- #1

Wminus

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Hi! When we model bloch-waves in a solid we assume that there exist some kind of periodic boundary conditions such that the wave function is periodic. In 1D, ##\psi(x)## repeats itself for every ##L##, ##\psi(x) = \psi(x+L)##, such as here:

OK, fine, we get pretty wave solutions if we assume the existence of the PBC.

Is ##L## just the wavelength?

OK, fine, we get pretty wave solutions if we assume the existence of the PBC.

**But what ##L##?**As far as I know the only repeating unit in a crystal is the Wieger Seitz cell, which is sized on the atomic scale.Is ##L## just the wavelength?