Conditional probability density functional theory

We present conditional probability (CP) density functional theory (DFT) as a formally exact theory. In essence, CP-DFT determines the ground-state energy of a system by finding the CP density from a sequence of Kohn-Sham (KS) calculations. Unlike standard KS-DFT, which relies on an accurate exchange-correlation (XC) functional to extract energies, CP-DFT only requires accurate self-consistent densities. A simple CP-DFT approximation yields usefully accurate results for two-electron ions and the hydrogen dimer. CP-DFT has no self-interaction error for one electron, and correctly dissociates H₂, both major challenges in standard KS-DFT.