DFT with effective potential expressed as a mapping of the external potential: Applications to closed‐shell molecules

Abstract

AbstractIn density functional theory (DFT), the Kohn–Sham (KS) potential VKS is expressed in terms of the ground‐state density. As a consequence, VKS does not always have the symmetry of the external potential V. The symmetry requirements are used to derive a noninteracting potential, VeK, as a direct mapping of the external potential V. This mapping gives the following VeK for molecules and solids: where Zi are the nuclear charges at positions Ri. An explicit form of the kernel K is given. Applications are made to small molecules (H2, LiH, BH, and H2O) in order to test its accuracy. The energies calculated were found to deviate very little from those of Hartree–Fock, as the relative deviation of the two energies, ΔE/E, was found to be of the order of 10−4. This accuracy is much higher than that of standard DFT in its local exchange potential approximation. This method is appropriate for large molecules, as it is much faster than HF and standard DFT, because the potential is known from the start. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005