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Title: Explaining and Fixing DFT Failures for Torsional Barrier
Most torsional barriers are predicted with high accuracies (about 1 kJ/mol) by standard semilocal functionals, but a small subset was found to have much larger errors. We created a database of almost 300 carbon–carbon torsional barriers, including 12 poorly behaved barriers, that stem from the Y═C—X group, where Y is O or S and X is a halide. Functionals with enhanced exchange mixing (about 50%) worked well for all barriers. We found that poor actors have delocalization errors caused by hyperconjugation. These problematic calculations are density-sensitive (i.e., DFT predictions change noticeably with the density), and using HF densities (HF-DFT) fixes these issues. For example, conventional B3LYP performs as accurately as exchange-enhanced functionals if the HF density is used. For long-chain conjugated molecules, HF-DFT can be much better than exchange-enhanced functionals. We suggest that HF-PBE0 has the best overall performance.  more » « less
Award ID(s):
1856165
PAR ID:
10220443
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
The journal of physical chemistry letters
Issue:
12
ISSN:
1948-7185
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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