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

Abstract

Three lowest diabatic potential energy surfaces for the F( 2 P) ϩ H 2 Van der Waals complex are derived from accurate ab initio calculations of the T-shaped (C 2v ) and collinear geometries (C ϱv ), 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 Legendrepolynomial 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

Long-Range Interaction in Some Simple Open-Shell Systems, Including Rare-Gas Sulfides: Features of Post-Adiabatic Potentials and Couplings

“…We do not discuss various 2D and 3D potential energy surfaces (PESs) that are available for the interactions between the F, Cl, O, and S atoms and the H 2 , HCl, HBr, and HI molecules and multidimensional (at most 12-dimensional) PESs for the interactions between these atoms and the methane molecule because such potentials cannot be used straightforwardly within the post-adiabatic iteration scheme. As an example, we mention the 3D ab initio Alexander−Stark−Werner PESs 20 for the F + H 2 system, the subsequent 2D and 3D PESs for this system with the improved long-range region, and very recent 3D ab initio diabatic PESs for the F + H 2 van der Waals complex …”

Interactions of 2P Atoms with Closed-Shell Diatomic Molecules: Alternative Diabatic Representations for the Electronic Anisotropy

“…Similarly, the diabatic coupling matrix elements used in that and subsequent references − are derived by exploiting the Hund's case (a) representation for electronic basis functions, which is obviously the best choice for systems in which the spin−orbit interaction is weak compared to potential anisotropy. , In the opposite limit of heavy X atoms, the Hund's case (c) coupling scheme offers more advantages, , and it is therefore desirable to obtain an analogue of the diabatic coupling matrix 14,15 in the Hund's case (c) representation.…”

Interactions in Open-Shell Clusters: Ab Initio Study of Pre-reactive Complex O(3P) + HCl

“…We have examined a number of pre-reactive complexes involving 2 P halogens interacting with closed-shell diatomics. − Ab initio calculations have been employed to characterize the Cl( 2 P) + HCl, Cl( 2 P) + H 2 , F( 2 P) + H 2 , and Br( 2 P) + H 2 8 complexes. The results were also reviewed recently .…”