Why do some bands go up

Let us take our beloved chain of hydrogen atoms in the Is state, to which we already owe so much (Fig. 9.13). 

When will the state of the chain have the lowest energy possible Of course, when all the atoms interact in a bonding, and not antibonding, way. This corresponds to Fig. 9.13.a (no nodes of the wave function). When, in this situation. 

Electronic Motion in the Mean Field Periodic Systems 

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