On the Correlation Potential in Frozen-Density Embedding Theory

The correlation functional E c[ρ] known in Levy’s constrained search formulation of density functional theory is also one of the components of the energy functional in frozen-density embedding theory (FDET) [ Wesolowski Phys. Rev. A, 77, 2008, 012504 ] if the embedded wave function has the single-determinant form. The relation between the FDET energy and quantities available from an auxiliary system is derived. In the auxiliary system, E c[ρ] and its functional derivative (correlation potential) are entirely neglected. The relation is exact up to the quadratic term in density changes caused by electron–electron correlation. It is discussed in view of its practical applications in modeling an electronic structure of embedded species.