Density-functional theory of polar insulators

R.W. Godby; X. Gonze; P. Ghosez

doi:10.1103/PhysRevLett.78.294

Density-functional theory of polar insulators

R.W. Godby, X. Gonze, P. Ghosez

Physics

Research output: Contribution to journal › Article › peer-review

Abstract

We examine the density-functional theory of macroscopic insulators, obtained in the large-cluster limit or under periodic boundary conditions. For polar crystals, we find that the two procedures are not equivalent. In a large-cluster case, the exact exchange-correlation potential acquires a homogeneous ``electric field'' which is absent from the usual local approximations, and the Kohn-Sham electronic system becomes metallic. With periodic boundary conditions, such a field is forbidden, and the polarization deduced from Kohn-Sham wavefunctions is incorrect even if the exact functional is used.

Original language	English
Pages (from-to)	294-297
Number of pages	3
Journal	Physical Review Letters
Volume	78
Issue number	2
DOIs	https://doi.org/10.1103/PhysRevLett.78.294
Publication status	Published - 13 Jan 1997

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AB - We examine the density-functional theory of macroscopic insulators, obtained in the large-cluster limit or under periodic boundary conditions. For polar crystals, we find that the two procedures are not equivalent. In a large-cluster case, the exact exchange-correlation potential acquires a homogeneous ``electric field'' which is absent from the usual local approximations, and the Kohn-Sham electronic system becomes metallic. With periodic boundary conditions, such a field is forbidden, and the polarization deduced from Kohn-Sham wavefunctions is incorrect even if the exact functional is used.

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