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Phys. Rev. Lett. 51, 1884–1887 (1983)

Physical Content of the Exact Kohn-Sham Orbital Energies: Band Gaps and Derivative Discontinuities

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John P. Perdew
Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, and Department of Physics and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118

Mel Levy
Department of Chemistry and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118

Received 17 June 1983; published in the issue dated 14 November 1983

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.

© 1983 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.51.1884
DOI:
10.1103/PhysRevLett.51.1884
PACS:
71.45.Gm, 71.25.Rk, 71.25.Tn
 
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