Calculating interior eigenvalues and eigenvectors with an implicitly restarted and a filter diagonalization method Original Research Article

We present a comparison of two iterative methods for calculating interior eigenvalue/eigenvector pairs for symmetric real matrices. The eigenvalue pattern of the test matrices we choose is typical of matrices used to calculate vibrational energy levels of molecules. In most cases we are unable to calculate interior eigenvalue/eigenvector pairs using the implicitly restarted method of Baglama et al. (1996). The filter diagonalization method of Mandelshtam and Taylor (1995) is extremely effective.