Abstract
The polarization dependence of the exchange-correlation (xc) energy functional of periodic insulators within Kohn-Sham (KS) density-functional theory requires a divergence in the xc kernel for small vectors q. This behavior, exemplified for a one-dimensional model semiconductor, is also observed when an insulator happens to be described as a KS metal, or vice versa. Although it can occur in the exchange-only kernel, it is not found in the usual local, semilocal, or even nonlocal approximations to KS theory. We also show that the test-charge and electronic definitions of the macroscopic dielectric constant differ from one another in exact KS theory, but are equivalent in the above-mentioned approximations.
- Received 27 February 1997
DOI:https://doi.org/10.1103/PhysRevB.56.12811
©1997 American Physical Society