Ab initio calculations and modeling of three‐dimensional adiabatic and diabatic potential energy surfaces of F(2P)···H2(1Σ+) Van der Waals complex

Abstract

AbstractThree lowest diabatic potential energy surfaces for the F(2P) + H2 Van der Waals complex are derived from accurate ab initio calculations of the T‐shaped (C2v) and collinear geometries (C∞v), 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 H2 stretching coordinate is also incorporated and analyzed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002