An accurate total energy density functional



We propose a new density functional for the evaluation of the total electronic energy by subtracting the Roothaan energy, i.e. the Hartree energy of the density residual, from the Hohenberg–Kohn–Sham (HKS) functional, which is normally used in self-consistent Kohn–Sham (KS) density functional theory (DFT) calculations. Because of the positive semi-definite nature of the Roothaan energy, the resulting Wang–Zhou (WZ) functional always produces a total energy lower than that from the HKS functional and usually converges to the exact total energy from below. Following the same spirit of the Zhou–Wang-λ (ZWλ) functional in the recently proposed orbital-corrected orbital-free (OO) DFT method (Zhou and Wang, J Chem Phys 2006, 124, 081107), we linearly mix the WZ functional with the HKS functional to allow further systematic error cancellations. The resulting Wang–Zhou-α (WZα) functional is compared with the ZWλ functional in OO-DFT calculations for systems within different chemical environment. We find that the optimal value of α for the WZα functional is more stable than that of λ for the ZWλ functional. This is because the WZ functional remedies the oscillatory convergence behavior of the Harris functional and renders the direct evaluation of α for the WZα functional more plausible in the application of the linear-scaling OO-DFT method for large systems. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007