THE OPTIMIZED EFFECTIVE POTENTIAL FOR ATOMS AND SEMICONDUCTORS

Given an n-electron Hamiltonian containing a potential operator such a s the Pock operator, the optimized effective potential (OEP) is that s imple multiplicative potential whose n lowest eigenfunctions minimize the expectation value of the Hamiltonian. Thus it is the exact Kohn-Sh am potential for that Hamiltonian. We discuss OEP calculations and the KLI approximation to it for atoms and semiconductors. Because the Poc k operator treats exchange exactly, all deviations from experimental e nergies are attributable to the use of approximate correlation energy density functionals whose shortcomings are discussed.