Electronic–geometric coupling in model reactive system

摘要

The equilibria in triatomic (collinear) reactive system are examined. The linear-response treatment of adjustments in the molecular electronic and geometrical degrees-of-freedom, determined from the chemical-potential (electronegativity) equalization principle, are predicted using the previously proposed analytical representation of the chemical hardness matrix in atomic resolution. The system relaxation is determined from the joint electronic–nuclear Hessian in the electron-following representation, defined by the corresponding second partials of the system Born–Oppenheimer potential. It includes the diagonal blocks of the electronic hardness tensor and geometric force constants, as well as the off-diagonal blocks of the nuclear Fukui function indices, which determine the coupling between the molecular electronic and geometrical structures. The latter are explicitly modelled using the canonical hardness tensor of the constituent atoms. This combined treatment explicitly accounts for the mutual coupling between the system charge distribution and its geometry. The molecular compliant descriptors, which determine the system minimum-energy coordinates, can be also generated using the inverse, electron-preceding representation.