Kersti Hermansson

This project deals with water molecules in condensed matter. OH vibrational frequencies, 1H NMR chemical shifts and XPS-measured O1s binding energies are widely used experimental techniques to elucidate structure and bonding, and for all three techniques, the spectroscopic signals relate to electron distributions, atomic charges and electronic shielding. At the same time, the physical phenomena behind these spectroscopies are very distinct. So do they respond in a similar fashion to surrounding perturbations, or not? Elucidating this question is Goal No. 1. I will address that question from a particular perspective, namely by comparing machine-learned 'structure=>spectra' models using a number of different structural (and some physical) descriptors, ranging from very simple ones (one H-bond distance) to very complex ones (like the elaborate MACE1 foundation model). Can the simplest structural fingerprints capture the effect of the surrounding molecules on the spectra? And at the other end of the complexity scale – can the models there provide any insight? Elucidating these questions is Goal No. 2. For the most advanced model in this study (MACE), we also compare some of the electronic features that are now incorporated in the newest MACE versions and exemplify how they compare with results from quantum-mechanical electronic structure calculations. That's Goal No. 3.