Recent Advances in Relativistic Density Functional Methods

Relativistic density functional theory has evolved into a powerful method for the electronic structure calculations of systems containing heavy elements. This article reviews the recent developments in this area but with the focus mainly on computational methodologies. The salient features of the Beijing Density Functional (BDF) program package are discussed. BDF is a code that can perform nonrelativistic and one-, two-, and four-component relativistic density functional calculations on medium-sized molecular systems with various functionals in most compact and yet sufficient basis set expansions. The necessity for merging the whole spectrum of the Hamiltonians into a single code is twofold: on the one hand, it facilitates direct and systematic comparisons between different Hamiltonians, and on the other hand, it facilitates the construction of hybrid relativistic and nonrelativistic methods for systems consisting of only a few heavy elements but many light ligands. Keywords: relativistic effects; density functional theory; hybrid relativistic and nonrelativistic methods; collinear; noncollinear; moment polarization; DKS; SEAX; ZORA; BDF