A symmetry-adapted Lanczos method for calculating energy levels with different symmetries from a single set of iterations

摘要

We present a symmetry-adapted Lancozos method that uses projection operators to calculate energy levels with different symmetries from a single sequence of matrix-vector products. Compared with the conventional Lancozos method, thismethod has the advantage that energy levels are computed more efficiently and with synmmetry labels. High-lying stretching energy levels of a coupled Morse oscillator Hamiltonian describing ~(28)SiH_4 are calculated to demonstrate the advantage of the symmetry-adapted method.