Hamiltonian diagonalization: computer program

As an example we consider a model Hamiltonian matrix in the case of orthogonal basis functions (S = I). The Hamiltonian for these systems is assumed to possess zero matrix elements Hy when / — y >4. It is trivial to modify the computer programs to consider a greater or lesser number of diagonals. The matrix half-bandwidth of 5 was chosen arbitrarily to demonstrate the technique for something other than the usual trivial case of the tridiagonal Hamiltonian of a one-dimensional system. 

Fig. 3.24 Spectrum of the naphthalene triplet state computed with D = 1,074 G, E = -164 G, [C.A. Hutchison, B.W. Mangum, J. Chem. Phys. 34, 908 (1961)]. A diagonalization of the spin Hamiltonien matrix. B second order perturbation treatment of the spin Hamiltonian. Spectra are adapted from http //www.esr-spectsim-softw.fr/programs with permission from Dr. C. Chachaty...

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