C parameters of the Buckingham potential are fixed to zero for all interactions involving Hp. This assumption has also been applied by previous authors . Although some of the AE datasets contain thiol structures with hydrogen bonded to sulphur, these datasets have been omitted from the initial testing done in this work, and thus no sulphur-bonded hydrogen is defined. Whether the sulphur-bonded and carbon-bonded hydrogens need to be distinguished is debatable and beyond the scope of this paper.