Calculation of clustered eigenvalues of large matrices using variance minimization method

The autoadjusting perturbation theory method is presented and developed to calculate eigenpairs of a square matrix. The procedures to simultaneously compute a cluster of eigenpairs by variance minimization are also given. Finally, numerical examples are reported. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1777–1785, 1998