PNNL

Abstract

Despite fundamental importance, the experimental characterization of the hydrogen bond network, particularly in multicomponent protic solutions, remains a challenge. Although recent work has experimentally validated that the oxygen K-edge X-ray ab- sorption spectra is sensitive to local hydrogen bond patterns in pure water and aqueous alcohol solutions, the generality of this observation is unknown - as is the sensitivity to the electronic structure of the alcohol cosolvent. In this work, we investigate the electronic structure of water solvated alcohol model geometries using energy specic time-dependent density functional theory to calculate oxygen K-edge X-ray excitations. We nd that the geometry of dangling hydrogen bonds in pure water is the main con- tributor to the pre-edge feature seen in the X-ray absorption spectra, agreeing with previous experimental and theoretical work. We then extend this result to solvated alcohol systems and observe a similar phenomenon, yet importantly, the increase of electron donation from alkyl chains to the alcohol OH group directly correlates to the strength of the core excitation on the dangling hydrogen bond model geometry. This trend arises from a stronger transition dipole moment due to electron localization on the OH group.