Modification of Davidson's method for the calculation of eigenvalues and eigenvectors of large real-symmetric matrices: ''root homing procedure''

Davidson's method for the iterative calculation of eigenvalues of large, real-symmetric matrices, which makes possible the direct determination of higher roots without knowledge of the exact lower ones, is modified to yield just such roots whose eigenvectors have a desired structure, that is, a desired set of dominant components. The algorithm is treated theoretically and applied to some configurational interaction (CI) problems. A study of the convergence behavior of Davidson's scheme is carried out. 4 tables