Multiconfigurational electronic wave functions without a reference configuration: Analysis of a simulated annealing strategy

Abstract

Multiconfigurational floating Gaussian electronic wave functions are obtained for a variety of 2-electron atoms and for H2. These correlated wave functions are unusual in that they are constructed without taking excitations from a reference configuration. The description of electron correlation, the degree to which the proper ground state symmetry is attained, and the behavior of wave functions obtained by simulated annealing as a function of nuclear position are analyzed for two types of basis functions, product Gaussians and a second type of basis function that explicitly includes electron correlation. This work is aimed toward applications in mixed quantum/classical condensed phase simulations. Several recent studies have used simulated annealing to build floating Gaussian electronic wave functions in condensed phase or cluster simulations. We analyze the ability of the simulated annealing method to follow the optimum, or near optimum wave functions as nuclear positions move.