Insufficient Hartree-Fock exchange in hybrid DFT functionals produces bent alkynyl radical structures

Victor B. Oyeyemi, John A. Keith, Michele Pavone, Emily A. Carter

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Density functional theory (DFT) is often used to determine the electronic and geometric structures of molecules. While studying alkynyl radicals, we discovered that DFT exchange-correlation (XC) functionals containing less than ∼22% Hartree-Fock (HF) exchange led to qualitatively different structures than those predicted from ab initio HF and post-HF calculations or DFT XCs containing 25% or more HF exchange. We attribute this discrepancy to rehybridization at the radical center due to electron delocalization across the triple bonds of the alkynyl groups, which itself is an artifact of self-interaction and delocalization errors. Inclusion of sufficient exact exchange reduces these errors and suppresses this erroneous delocalization; we find that a threshold amount is needed for accurate structure determinations. Below this threshold, significant errors in predicted alkyne thermochemistry emerge as a consequence.

Original languageEnglish (US)
Pages (from-to)289-293
Number of pages5
JournalJournal of Physical Chemistry Letters
Volume3
Issue number3
DOIs
StatePublished - Feb 2 2012

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Physical and Theoretical Chemistry

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