The Correlation Effects in Density Functional Theory Along the Dissociation Path

Abstract

Abstract Standard, density-dependent, density functional theory (DFT) and ab initio DFT (in a context of optimized effective potential—OEP) calculations for a few weakly interacting systems (He 2 , Ne 2 , ArNe) at nonequilibrium geometries up to near dissociation limit were performed. Results of this study are reported and analyzed in terms of correlation and exchange-correlation potentials, correlated densities, and interaction energy curves. The orbital-dependent second-order OEP methods (i.e., OEP2-sc, OEP2-SOSb) are directly compared with a few standard DFT functionals (i.e., SVWN5, BLYP, PBE). All examined functionals yield stable (regarding shape and amplitude) Kohn–Sham exchange-correlation potentials and correlated densities along the dissociation path, but it is found that the standard DFT methods are extremely inaccurate in this area and provide erroneous predictions for formation of weakly bound states. In contrast, the OEP methods provide qualitatively and quantitatively correct results, particularly regarding the description of weakly bound states.