A SPECTRAL FILTER APPROACH TO THE WAVE OPERATOR TREATMENT OF LARGE MATRIX EIGENVALUE PROBLEMS

A Green function filter operator (H-E.1)(-1) is used within a wave ope rator iterative method for the computation of interior eigenvalues of large Hamiltonian matrices. Test calculations on a coupled oscillator system show a significant improvement in the convergence of the wave o perator iterative method when the filter is used with a one-dimensiona l active space. Less convincing results are obtained with multidimensi onal active spaces involving several states in near resonance; other f ilter functions such as (H-E.1)(-2) seem to be more suitable for this case. (C) 1996 American Institute of Physics.