Convergence of diabatic to adiabatic scattering calculations

We investigate the convergence of diabatic scattering representations that make use of the commonly applied closure relation (which eliminates first and second derivative coupling terms from the Schrödinger equation for the scattering wave function) to the adiabatic scattering formulations from which they are derived (wherein the internal basis states depend upon the collision coordinate). Numerical examples using a simple model of electron transport in a tapered waveguide are presented. The convergence of the diabatic to the adiabatic results with respect to the number of basis states is extremely slow. We discuss the significance of these findings to atomic and molecular scattering calculations.