Supplementary Information for Prof Leonhard’s group submission for HyDRA challenge

This document contains supplementary information of Prof Leonhard’s group submission to HyDRA challenge [DOI:10.26434/chemrxiv-2021-w8v42] on hydrogen-bonded clusters. Conformer search was conducted using CREST 2.11 [DOI:10.1039/C9CP06869D, DOI:10.1021/acs.jctc.9b00143, DOI:10.1039/d1sc00621e] at the GFN2-xTB [DOI:10.1021/acs.jctc.8b01176] level with default settings. The lowest energy conformer obtained was then optimized using Gaussian 16 at the b2plyp/aug-cc-pvtz level of theory with Grimme’s dispersion (gd3bj key word in Gaussian) [DOI:10.1063/1.3382344] and an extremely fine integral grid (int=grid=199974). Optimization was carried out using initial force constants from previous b2plyp/aug-cc-pvdz calculations. The frequency calculation at b2plyp/aug-cc-pvtz level was carried out with selected anharmonic modes. These modes were chosen based on visual inspection of normal modes mainly involving motion of the donor hydrogen. We optimized and calculated the frequencies for the clusters of water and one of the four molecules: Formaldehyde (FAH), Tetrahydrothiophene (THF), Tetrahydrofuran (THT) and Trifluroethan-1-ol (TFE).