X-ray absorption of liquid water by advanced ab initio methods

TL;DR

This study combines advanced ab initio molecular dynamics and GW-based electron excitation theory to accurately compute liquid water's X-ray absorption spectra, achieving better agreement with experiments.

Contribution

It introduces a comprehensive approach integrating van der Waals interactions, hybrid functionals, and an enhanced screening approximation for improved spectral predictions.

Findings

Spectra align closely with experimental data

Hydrogen bonds are effectively softened in the model

Spectral broadening matches experimental observations

Abstract

Oxygen K-edge X-ray absorption spectra of liquid water are computed based on the configurations from advanced ab initio molecular dynamics simulations, as well as an electron excitation theory from the GW method. One one hand, the molecular structures of liquid water are accurately predicted by including both van der Waals interactions and hybrid functional (PBE0). On the other hand, the dynamic screening effects on electron excitation are approximately described by the recently developed enhanced static Coulomb hole and screened exchange approximation by Kang and Hybertsen [Phys. Rev. B 82, 195108 (2010)]. The resulting spectra of liquid water are in better quantitative agreement with the experimental spectra due to the softened hydrogen bonds and the slightly broadened spectra originating from the better screening model.