The first HyDRA challenge for computational vibrational spectroscopy

Abstract

Vibrational spectroscopy in supersonic jet expansions is a powerful tool to assess molecular aggregates in close to ideal conditions for the benchmarking of quantum chemical approaches. The low temperatures achieved as well as the absence of environment effects allow for a direct comparison between computed and experimental spectra. This provides potential benchmarking data which can be revisited to hone different computational techniques, and it allows for the critical analysis of procedures under the setting of a blind challenge. In the latter case, the final result is unknown to modellers, providing an unbiased testing opportunity for quantum chemical models. In this work, we present the spectroscopic and computational results for the first HyDRA blind challenge. The latter deals with the prediction of water donor stretching vibrations in monohydrates of organic molecules. This edition features a test set of 10 systems. Experimental water donor OH vibrational wavenumbers for the vacuum-isolated monohydrates of formaldehyde, tetrahydrofuran, pyridine, tetrahydrothiophene, trifluoroethanol, methyl lactate, dimethylimidazolidinone, cyclooctanone, trifluoroacetophenone and 1-phenylcyclohexane-cis-1,2-diol are provided. The results of the challenge show promising predictive properties in both purely quantum mechanical approaches as well as regression and other machine learning strategies.

Of Resonances and Radicals – Hydrate Studies for Benchmarking

“…A lot of benchmarking suited data was produced, ranging from neutral hydrate cluster from the HyDRA blind challenge [84] to more complex systems as the jet cooled gas phase spectra of hydrates of stable radicals [20] or the b2lib resonance [14]. For many of the systems also isotopic data is available.…”

“…The procedure that was followed for the so-called HyDRA blind challenge is described in [29,83]. The key aspects will be described here as well as the experimental results (available as electronic supplement in [84] and [85]), while the analysis of the performance of the participating groups can be found in the corresponding publication [84]. The analysis and evaluation of the theory submissions was mostly conducted by Prof. Dr. Ricardo Mata and Dr. Benjamin Schröder.…”

“…5.4: Experimental details on the spectroscopic data on formaldehyde (BC02) water giving the spectral identifiers ([yyyymmdd]-[averaged spectra]), the partial pressures, stagnation pressure and color in the spectrum. [84] The water spectra are taken from [2].…”

“…Their setup is allowing a size selective investigation of the complex using an IR-UV double resonance method [128,129]. More information can be found in the Supplement of [84].…”

“…5.11: IR depletion spectrum of BC36+water using 16 O-and 18 O-water to securely assign the OH stretching vibrations of water. [84] 5.2.10 2,2,2-Trifluoroethan-1-ol -BC38…”