Orbital‐free effective embedding potential: Density‐matrix functional theory case

Minimization of the Hohenberg–Kohn total energy functional E HK [ρ] in the presence of the constraint ρ − ρ B ≥ 0, where ρ B is some arbitrarily chosen electron density comprising integer number of electrons is considered. To access better numerical accuracy of approximations to E HK [ρ] in practice, the search for optimal ρ − ρ B is performed using auxiliary quantities such as orbitals of a reference system of non‐interacting electrons [Wesolowski and Warshel, J Phys Chem 1993, 97, 8050] or a wavefunction‐like object corresponding to interacting electrons [Wesolowski, Phys Rev A 2008, 77, 012504]. In both cases, the condition ρ − ρ B ≥ 0 leads to a local potential ( orbital‐free effective embedding potential ) of the same general form if expressed by means of universal density functionals. In this work, it is shown that the same local potential is obtained if the search for optimal ρ − ρ B is performed among one‐particle reduced density matrices. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009