Sign-consistent dynamical couplings between ab initio three-center wave functions

We present a method to ensure the sign consistency of dynamical couplings between ab initio three-center wave functions. The method also allows to systematically diabatize avoided crossings between two potential energy surfaces, including conical intersections. Illustrations are presented for H-3(+), LiH2+, and NH25+ quasimolecules. (C) 2004 American Institute of Physics.