Scalar-relativistic LCGTO DFT calculations for atoms using the Douglas-Kroll transformation

Abstract

Haberlen and Rosch (HR) demonstrated [Chem. Phys. Lett. 199, 491 (1992)] the feasibility of performing scalar-relativistic, density functional theory (DFT) linear combination of Gaussian-type orbitals–fitting function (LCGTO-FF) calculations on clusters of atoms using an “incomplete” Douglas–Kroll transformation. Some of the approximations used in their multiatom calculations have not yet been fully explored for isolated atoms, especially the neglect of matrix elements involving vector products of the momentum and the use of fitting functions. In this investigation, scalar-relativistic LCGTO calculations (without fitting functions) were carried out at four levels of approximation, including that employed by HR, for four atoms: Ce, Au, Pb, and Pu. The results of these calculations suggest that the HR approximation should be applicable to atoms through the light actinides, so long as spin–orbit effects are unimportant. A comparison of very large basis-set results with results obtained using ordinary-size basis sets indicates that the valence (bonding) states from scalar-relativistic LCGTO-FF calculations should be no more sensitive to the orbital basis-set size than are their nonrelativistic counterparts. Published 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 565–574, 1997