n-Alkane isodesmic reaction energy errors in density functional theory are due to electron correlation effects.
The isodesmic reaction energies of n-alkanes to ethane, which have so far been known to give systematic errors in standard DFT calculations, are successfully reproduced by SCS-MP2 and dispersion-corrected double-hybrid functionals. The failure of conventional DFT is not due to the lack of long-range exchange interactions but results from an inaccurate account of medium-range electron correlation that is attractive for 1,3-interactions (proto-branching). Highly accurate CCSD(T)/CBS data are provided that are recommended in thermochemical benchmarks.
Grimme
Stefan
S
Organisch-chemisches Institut, Westfälische Wilhelms Universität Münster, Corrensstr. 40, 48149 Münster, Germany. grimmes@uni-muenster.de