CALCULATION OF ELECTRIC-DIPOLE TRANSITION MOMENTS USING QUASI-DEGENERATE VARIATIONAL PERTURBATION-THEORY AND AVERAGED COUPLED-PAIR FUNCTIONAL THEORY

Results are reported from calculations of electric dipole transition moments for various electronic transitions in Be, CH2, and AlH using multireference singles and doubles configuration interaction, quasi-degenerate variational perturbation theory, and multireference averaged coupled pair functional theory. A simple normalization scheme is used for the quasi-degenerate variational perturbation theory and multireference averaged coupled pair functional theory wave functions. In all cases, comparison is made with full configuration interaction results in the valence space. For Be and CH2, all methods are of comparable quality in calculating the transition moments and excitation energies, with averaged coupled-pair functional theory yielding slightly quicker convergence of the excitation energies and transition moments in most cases. For AlH, multireference singles and doubles configuration interaction is somewhat more accurate for the calculation of the transition moment. Factors that affect the accuracy of the methods are discussed. (C) 1994 John Wiley & Sons, Inc.