Physical Content of the Exact Kohn-Sham Orbital Energies: Band Gaps and Derivative Discontinuities
John P. PerdewInstitute for Theoretical Physics, University of California, Santa Barbara, California 93106, and Department of Physics and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118Mel LevyInstitute for Theoretical Physics, University of California, Santa Barbara, California 93106, and Department of Physics and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118
1983en
ABI
Annotatsiya
The local-density approximation for the exchange-correlation potential understimates the fundamental band gaps of semiconductors and insulators by about 40%. It is argued here that underestimation of the gap width is also to be expected from the unknown exact potential of Kohn-Sham density-functional theory, because of derivative discontinuities of the exchange-correlation energy. The need for an energy-dependent potential in band theory is emphasized. The center of the gap, however, is predicted exactly by the Kohn-Sham band structure.
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