Individual clusters as a bridge to predict IR spectra of mixtures

Scaling factors (Sfs) derived from pristine clusters are shown to be transferable for predicting the infrared spectra of molecular mixtures. The vibrational spectra of the , , , and clusters, and their HCN mixtures at different concentrations, were calculated using GFN2-xTB method. Frequency- and intensity-dependent SFs were calibrated against experimental cryogenic spectra of the pristine clusters and subsequently applied to mixtures, employing concentration-weighted factors for intermolecular regions and molecule-specific factors for intramolecular modes. The scaled spectra reproduce experiments with fidelity, establishing pristine-cluster SFs as transferable and computationally inexpensive for modeling mixtures infrared spectra, with relevance to astrophysical ice observations. • IR spectra of the HCN, H2O, CH3OH, and CO2 pristine clusters and their HCN mixtures were calculated. • Weighted scaling factors determined from the pristine clusters are used to predict mixtures’ IR spectra. • Scaled IR spectra accurately reproduce all concentrations of the experimental data. • The proposed methodology is relevant for identifying IR spectra in astrophysical environments.