For FAH as the simplest molecule in the test set, it is long established by theory and experiment that water coordinates asymmetrically. The OH stretching vibration which is of interest in this challenge has been determined in matrix isolation , but to the best of our knowledge not in the gas phase without environmental influence. In cryogenic matrices, split signals were found (3580, 3585 cm -1 in neon and argon, 3573, 3578 cm -1 in a nitrogen matrix).