Inclusion of relativistic effects in Gaussian-basis density functional calculations for extended systems

Non-perturbative calculation of the scalar relativistic contributions to the density functional total energy and one-electron energies of extended systems until recently has been via exploitation of the features of cellular basis sets (the Koelling-Harmon scheme and cousins) to achieve the decoupling of large and small components. Cellular basis sets are relatively uncommon in quantum chemistry codes; Gaussian-type orbitals are the de facto standard. Among the various order-by-order decouplings used for molecular calculations in quantum chemistry, the Douglas-Kroll transformation has advantages which have brought it to prominence. Here we review the first extension of that procedure to an all-electron, linear combination of Gaussian-type-orbitals, fitting function (LCGTO-FF) methodology for DFT calculations on crystals and ordered films. To show the power and accuracy of the method, we summarize results for Au, Mo, Th, and Pu. In general, values from the Gaussian methodology and from cellular-basis, all-electron, scalar-relativistic density functional codes are essentially indistinguishable. In every case of a difference compared to previously published results, the prediction of the Gaussian methodology has been confirmed by an independent high-quality cellular-based calculation. These outcomes verify that, for the first time, a single, consistent, systematic, first-principles, all-electron, full-potential DFT technique is available for prediction of the properties of complex crystalline, slab, ordered polymer, and cluster/molecule systems that contain heavy elements, all devoid of potentially troublesome algorithmic inconsistencies. (C) 2000 Elsevier Science B.V. All rights reserved.