Hückel method

The Hückel method is used to evaluate energy levels disposition in a molecule, following the linear combination of atomic orbitals theory (MO-LCAO). We'd have to solve . We do recall the diagonal elements of and its off-diagonal elements. Hence:

Hence: , and all the other elements are zeros, except for the case of circular molecules, where also the matrix element that correspond to the first/last atom bound is equal to . Energy levels now can be found solving , that is:

Recall and solve in order to find energy levels. Remember that generally , and it is called hopping parameter.