The ever-increasing accuracy of quantum chemical calculations calls for subtle experimental benchmarks to test their systematic performance. Solvation is a field where subtleties matter, because the bulk effect is the sum over many individual (cooperative) contributions, such that even small errors may add up. Size matters, as many accurate methods scale unfavourably with the number of electrons. Zero point energy is often a game killer, because it is unavoidable in experiment and hard to treat beyond the harmonic approximation by theory. A broad data base ultimately matters, because fortuitous error compensation is a frequent threat to our judgement.

Furan solvation challenge

We want to kick off a medium- to long-term benchmarking challenge, starting with the methanol solvation preference of 2,5-dimethylfuran, which was recently shown to be subtle, but experimentally tractable (doi:10.1039/c6cp05413g). Furan offers a planar scaffold with many potential modification options via alkyl and other substitution. Methanol can also be easily modified by alkylation. The methanol-furan contact pair is small enough to leave some hope for future anharmonic treatments of zero point energy, but large enough to render this a major challenge for relative energy predictions on the sub-kJ/mol scale. The anharmonic effects appear small enough or sufficiently compensating to be negligible in the first round of this challenge. As electronic structure treatments mature, persistent deviations between experiment and harmonic theory may even become interpretable in terms of such anharmonic effects.

The challenge starts on November 1, 2016. For more information, visit the Challenge page.