Density functional theory for d‐ and f‐electron materials and compounds

The fundamental requirements for a computationally tractable Density Functional Theory‐based method for relativistic f‐ and (nonrelativistic) d‐electron materials and compounds are presented. The need for basing the Kohn–Sham equations on the Dirac equation is discussed. The full Dirac scheme needs exchange‐correlation functionals in terms of four‐currents, but ordinary functionals, using charge density and spin‐magnetization, can be used in an approximate Dirac treatment. The construction of a functional that includes the additional confinement physics needed for these materials is illustrated using the subsystem‐functional scheme. If future studies show that a full Dirac, four‐current based, exchange‐correlation functional is needed, the subsystem functional scheme is one of the few schemes that can still be used for constructing functional approximations. © 2016 Wiley Periodicals, Inc.