# Kronig Penney Model

We know electron has potential energy as shown in fig 1 .
Now in my book ( Charles Kittel) it is written that kronig and penney modified this to be a square potential as shown in fig 2.
How is the potential in fig 2( inkronig penney model) drawn to be positive (Vo) if in figure 1 it is shown to be negative ( and rightly so,as in my opinion, potential energy of electron should be negative in presence of positive charge)?
Will the Schrodinger eqn solutions not change in the resp. regions if we arbitrarily change the sign of the potential energy to positive as has been done in kittel?
And one note: http://en.wikipedia.org/wiki/Partic...tice_(periodic_potential)#Kronig-Penney_model :here Vo is taken to be negative and hence Schrodinger eqn soln is different in -b<x<0 from the one given in Kittel.Is this and kittel both right?
Fig 1 and fig2 are attached

#### Attachments

• fig 1.jpg
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• fig 2.gif
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