Spin-orbit coupling effects in dihydrides of third-row transition elements.II. Interplay of nonadiabatic coupling in the dissociation path ofrhenium dihydride

摘要

This is the second paper in a series of investigations on spin-orbit coupling (SOC) effects indihydrides of third-row transition elements. The dissociation path of rhenium dihydride wasexplored using the multiconfiguration self-consistent-field method followed by diagonalization ofSOC matrices, in which the Stevens-Basch-Krauss-Jasien-Cundari (SBKJC) basis sets wereemployed after adding one set of polarization functions for each atom. The most stable rheniumdihydride has a linear structure and its ground state is ~6Σ_g~+.BothC2vand Csdissociation paths intoa Re atom and a hydrogen molecule (Re(~6S) +H_2(~1Σ_g~+)) were explored on the potential energycurves of low-lying states. A relatively high energy barrier was obtained along the C2v path and twoconical intersections were found at the H–Re–H angles of 29.8° and 96.1° along the C2v path. Sinceit was revealed that the geometrical deformation to Cs symmetry at the H–Re–H angle of 29.8° doesnot provide explicit lowering of the energy barrier for the dissociation, even after consideringnonadiabatic couplings (NACs) in the neighborhood of the conical intersections, it can be concludedthat the most feasible path is hopping from the lowest 6A1 state to the lowest 6B2 state at theH-Re-H angle of 96.1° followed by hopping from the lowest 6B2 state back to the lowest 6A1 stateat the H-Re-H angle of 29.8°, where the latter crossing point is the highest in energy along this path.Thus, when the molecular system can reach the areas of these crossing points, the molecular systemhops from one of the states to another owing to NAC or SOC effects; especially, SOC effectsbecome important at the crossing point with C_(2v)symmetry.