Convergence of the multicenter B-spline DFT approach for the continuum

Abstract

A multicenter approach for the calculation of the electronic continuum spectrum based on the B-spline functions and employing a Kohn–Sham density functional hamiltonian is introduced. The method is based on a large expansion on the origin, supplemented by a limited number of off-center functions located on the positions of the nuclei. The method has been applied to study the photoionization of Cl2, of the model system (CO)2 and of Cr(CO)6. The method has proven very efficient: the convergence to the exact results is obtained with matrices which are much smaller than those involved in one center expansion calculations and the algorithm is numerically stable up to very high photoelectron energies (200 eV). The importance of the asymptotic moment basis set requirement is pointed out and rationalized with the help of a simple model. Preliminary calculations on Cr(CO)6 are then presented and their convergence discussed.