VALIDITY CRITERIA FOR ROTOR VIBRATOR AND INDEPENDENT-PARTICLE MODELS OF ATOMS - OVERLAPS, OSCILLATOR-STRENGTHS, AND ANGULAR DEVIATIONS

A comparison is made of Hartree-Fock, independent-particle (HF) and collective, molecule-like rotor-vibrator (RV)models for atoms with two valence electrons. The two models are constructed from the same pseudopotential Hamiltonian. The criteria for the comparison are (a) overlap with well-converged configuration interaction (CI) wave functions, (b) comparison of oscillator strengths with values from well-converged Cl functions (and, wherever possible, from experiment), and (c) comparison of the root-mean-square deviation of the angular distribution, i.e., ([theta12] 2 - [theta12(2)])1/2. In the comparison of the overlaps, neither model is obviously superior to the other. The RV wave functions yield better oscillator strengths in more cases than the HF functions, despite the results of the overlap calculations. Qualitative comparisons of the spatial distributions of probability density suggest that the RV functions have angular distributions much more like the CI functions than do the HF functions. A simple model calculation of the effect of a small amount of configuration mixing elucidates this similarity. A brief comparison is made of energy optimization and overlap optimization.