Structural manifestation of the delocalization error of density functional approximations: C(4N+2) rings and C(20) bowl, cage, and ring isomers.
Abstract
The ground state structure of C(4N+2) rings is believed to exhibit a geometric transition
from angle alternation (N < or = 2) to bond alternation (N > 2). All previous density
functional theory (DFT) studies on these molecules have failed to reproduce this behavior
by predicting either that the transition occurs at too large a ring size, or that
the transition leads to a higher symmetry cumulene. Employing the recently proposed
perspective of delocalization error within DFT we rationalize this failure of common
density functional approximations (DFAs) and present calculations with the rCAM-B3LYP
exchange-correlation functional that show an angle-to-bond-alternation transition
between C(10) and C(14). The behavior exemplified here manifests itself more generally
as the well known tendency of DFAs to bias toward delocalized electron distributions
as favored by Huckel aromaticity, of which the C(4N+2) rings provide a quintessential
example. Additional examples are the relative energies of the C(20) bowl, cage, and
ring isomers; we show that the results from functionals with minimal delocalization
error are in good agreement with CCSD(T) results, in contrast to other commonly used
DFAs. An unbiased DFT treatment of electron delocalization is a key for reliable prediction
of relative stability and hence the structures of complex molecules where many structure
stabilization mechanisms exist.
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https://hdl.handle.net/10161/3322Published Version (Please cite this version)
10.1063/1.3445266Publication Info
Heaton-Burgess, Tim; & Yang, Weitao (2010). Structural manifestation of the delocalization error of density functional approximations:
C(4N+2) rings and C(20) bowl, cage, and ring isomers. J Chem Phys, 132(23). pp. 234113. 10.1063/1.3445266. Retrieved from https://hdl.handle.net/10161/3322.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Weitao Yang
Philip Handler Distinguished Professor of Chemistry
Prof. Yang, the Philip Handler Professor of Chemistry, is developing methods for quantum
mechanical calculations of large systems and carrying out quantum mechanical simulations
of biological systems and nanostructures. His group has developed the linear scaling
methods for electronic structure calculations and more recently the QM/MM methods
for simulations of chemical
reactions in enzymes.

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