Towards Efficient Orbital-Dependent Density Functionals for Weak and Strong Correlation

We present a new paradigm for the design of exchange-correlation functionals in density-functional theory. Electron pairs are correlated explicitly by means of the recently developed second order BetheGoldstone equation (BGE2) approach. Here we propose a screened BGE2 (sBGE2) variant that efficiently regulates the coupling of a given electron pair. sBGE2 correctly dissociates H-2 and H-2(+), a problem that has been regarded as a great challenge in density-functional theory for a long time. The sBGE2 functional is then taken as a building block for an orbital-dependent functional, termed ZRPS, which is a natural extension of the PBE0 hybrid functional. While worsening the good performance of sBGE2 in H-2 and H-2(+), ZRPS yields a remarkable and consistent improvement over other density functionals across various chemical environments from weak to strong correlation.