Energy spectrum of a crystal lattice electron

Energetically speaking, a crystal lattice has a periodic potential, and the issue we are facing is to know how an electron behaves in such a lattice. 

In theory, it would also be necessary to take into accormt the movement of all the other electrons. However, for the sake of simplicity, we will adopt a ID lattice model, and we will suppose that the movement of the electron is not affected by the presence of other electrorrs. This simplified model, though, is a good means of describing the electronic properties that interest us in this book. This model will particrrlarly allow us to demonstrate the concept of the electron s effective mass. 

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