Finally, we have the best set of values under this category, the FA1 submission. It falls close to FA3 for the best predictions, with the largest errors for MLA and THF, 101 and 76 cm -1 in absolute deviations. The total RMSD falls significantly once the two outliers are removed (RMSD of 27 cm -1 ). It is a unique set of calculations within the challenge. The authors carried out adiabatic ab initio molecular dynamics at the B3LYP-D3(BJ)/aug-cc-pVTZ level of theory. The fundamentals were taken from the power spectrum which is obtained by Fourier transform of the velocity autocorrelation function. Further details to the method are available in the corresponding Supplementary Information. The single trajectories were started from optimised minima which fall in good agreement with the best predictions available, aside from a small difference in the conformation of the PCD hydrate. The source of the deviations should not be linked to the starting structures or the initial momenta. One should note that for this particular submission, the results for the training set were significantly better than for the test set, 18 vs. 47 cm -1 . Most of this difference is due to the two aforementioned outliers, and which the authors anticipated as problematic. MLA and THF spectra were characterized by complex power spectra and more investigations should have been undertaken to best identify the target spectroscopic signal. Clearly this task is eased in the case of the training set.