Calculation and interpretation of classical turning surfaces in solids

Kaplan, Aaron D.; Clark, Stewart J.; Burke, Kieron; Perdew, John P.

doi:10.1038/s41524-020-00479-0

Calculation and interpretation of classical turning surfaces in solids

Kaplan, Aaron D.; Clark, Stewart J.; Burke, Kieron; Perdew, John P.

Authors

Aaron D. Kaplan

Professor Stewart Clark s.j.clark@durham.ac.uk
Professor

Kieron Burke

John P. Perdew

Abstract

Classical turning surfaces of Kohn–Sham potentials separate classically allowed regions (CARs) from classically forbidden regions (CFRs). They are useful for understanding many chemical properties of molecules but need not exist in solids, where the density never decays to zero. At equilibrium geometries, we find that CFRs are absent in perfect metals, rare in covalent semiconductors at equilibrium, but common in ionic and molecular crystals. In all materials, CFRs appear or grow as the internuclear distances are uniformly expanded. They can also appear at a monovacancy in a metal. Calculations with several approximate density functionals and codes confirm these behaviors. A classical picture of conduction suggests that CARs should be connected in metals, and disconnected in wide-gap insulators, and is confirmed in the limits of extreme compression and expansion. Surprisingly, many semiconductors have no CFR at equilibrium, a key finding for density functional construction. Nonetheless, a strong correlation with insulating behavior can still be inferred. Moreover, equilibrium bond lengths for all cases can be estimated from the bond type and the sum of the classical turning radii of the free atoms or ions.

Citation

Kaplan, A. D., Clark, S. J., Burke, K., & Perdew, J. P. (2021). Calculation and interpretation of classical turning surfaces in solids. npj Computational Materials, 7, Article 25. https://doi.org/10.1038/s41524-020-00479-0

Journal Article Type	Article
Acceptance Date	Dec 12, 2020
Online Publication Date	Feb 1, 2021
Publication Date	2021
Deposit Date	Jun 4, 2021
Publicly Available Date	Jun 4, 2021
Journal	npj Computational Materials
Publisher	Nature Research
Peer Reviewed	Peer Reviewed
Volume	7
Article Number	25
DOI	https://doi.org/10.1038/s41524-020-00479-0

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