System ΔΔG298 NICS(0) Δr (Å)
Cs R=H 0.0 -14.9 0.014
D2 R=H 15.0 -18.3 0.010
Cs R=F 3.0 -4.6 0.117
D2 R=F 0.0 -15.9 0.012

The D2 form is a stable minimum up to e.g. B3LYP and KMLYP/cc-pVQZ. CCSD(T) is untested!
[14]Annulene: A stable minimum
with D2 Symmetry

Nucleus-Independent Chemical Shifts (NICS): P. von R. Schleyer, C. Maerker, A. Dransfeld, H. Jiao, and N. J. R. van Eikema Hommes, J. Am. Chem. Soc.; 1996; 118, 6317 - 6318. DOI: 10.1021/ja960582d
© H. S. Rzepa, 2006.