PHYS2170 Lecture Notes - Lecture 11: Periodic Function, Electric Field, Semimetal
4 Aug 2019
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Atom has the same wavefunction at a far distance from each other. As the atoms come towards each other, their wavefunctions begin to overlap: pauli"s exclusion principle begins to apply. When two atoms approach each other, the wavefunctions of the outermost electrons overlap: taking hydrogen as an example, the two 1s states, which have the same energy. When atoms are far apart, they split into two states of different energy in keeping with the pauli exclusion principle (figure a) If six atoms are brought together, each state splits into six states of different energy (figure b) If n atoms are brought together, each state splits into n states of different energy (i. e. the number of states equals the number of atoms) because of the overlapping wavefunctions. Since a sample of solid contains a large number of atoms, each state splits into energy levels so close together that energy bands are formed.
