Ab initio calculations and modeling of three-dimensional adiabatic and diabatic potential energy surfaces of F(P-2)center dot center dot center dot H-2((1)Sigma(+)) Van der Waals complex

摘要

Three lowest diabatic potential energy surfaces for the F(P-2) + H-2 Van der Waals complex are derived from accurate ab initio calculations of the T-shaped (C-2v) and collinear geometries (C-infinityv), at the coupled-cluster single, double, and noniterative triple excitations [CCSD(T)] level of theory with a large basis set. For the intermediate geometries the angular dependence is modeled by a simple Legendre-polynomial interpolation. The nonadiabatic coupling (off-diagonal derivative) matrix element, and the fourth, off-diagonal, diabatic surface are determined by separate multireference configuration interaction (MR-CI) calculations with a somewhat smaller basis set. Three adiabatic potential energy surfaces (PESs) are also obtained, by diagonalizing the total Hamiltonian in the diabatic basis. Both the nonrelativistic and relativistic (including spin-orbit coupling) PESs are evaluated. They are found to be in very good agreement with the entrance channel of the ASW PESs (Alexander, Manolopoulos, and Werner, J Chem Phys 2000, 113, 11084). The dependence of the PESs on the H-2 stretching coordinate is also incorporated and analyzed. (C) 2002 Wiley Periodicals, Inc. [References: 51]