High-level ab initio calculations of the torsional potential of glyoxal

The torsional barrier of glyoxal has been extensively studied using state-of-the-art ab initio methodologies ranging from Hartree–Fock (HF) and Möller–Plesset theories up to several developments of the coupled-cluster (CC) formalism, namely: CCD, CCSD, CCSD(T), BD and BD(T). We present a thorough discussion about the influence of the basis set size on the results, as well as a comparison between all the theories employed. The values obtained from the CCSD or CCSD(T) treatment achieve the so-called `calibration accuracyʹ (±1 kJ/mol) from which an extremely accurate torsional potential has been derived.