✍ Scribed by Jérôme Rey; Andreas Savin
No coin nor oath required. For personal study only.
Adding a nonlocal operator to the true Hamiltonian is used to define an Ž . adiabatic coupling between a noninteracting e.g., Kohn᎐Sham reference system and the real one. By using the Hellmann᎐Feynman theorem, it is shown that when the operator Ž . added is shifting upward the virtual noninteracting levels the correlation energy is related to the number of electrons displaced into the virtual levels. To construct approximations, calculations were performed for the uniform electron gas. The expectation that atomic systems would behave locally like a uniform electron gas with the unoccupied levels shifted up by a constant close to the atomic excitation energies is not confirmed by exploratory calculations on atoms. Some perturbation theory expressions are also given and suggest an approach to self-interaction free-correlation energy functionals. ᮊ 1998
📜 SIMILAR VOLUMES
The vertical iordzaticn potentials from 9-22 eV for ethylene, cycfoprppene, cyclobutene and methylene ~e~apropa~e are correlated with t%e ab initio 431G molecular orbital energies by -IP = 0.772 Ehfo -2.22 with an rms error of 0.2 eV. The result is related to the reorganization and correlation energ