Eigenvector expansion Hamiltonian diagonalization

Again, the expansions of the corresponding eigenvectors on the basis in which the quantum harmonic Hamiltonian of the H-bond bridge is diagonal, are... 

For short Cl expansions one could simply construct and diagonalize the Hamiltonian matrices For longer Cl expansions a direct Cl procedure must be employed. Here the desired eigenvectors are obtained iteratively without explicitly calculating and storing the Hamilton matrix. The basic operation in a direct Cl iteration is the evaluation of the residual vectors ... 

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