The Douglas-Kroll-Hess electron density at an atomic nucleus
The picture-change error on Douglas-Kroll-Hess (DKH) electron densities at atomic nuclei is analyzed in detail to high orders. Our results demonstrate that high-order DKH transformations of especially the property operator are needed to obtain converged results. However, if the convergence properties are discussed in terms of a relative error a fast convergence of the picture-change corrected DKH