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Title: Relationship between x-ray emission and absorption spectroscopy and the local H-bond environment in water

Here, the connection between specific features in the water X-ray absorption spectrum and X-ray emission spectrum (XES) and the local H-bond coordination is studied based on structures obtained from path-integral molecular dynamics simulations using either the opt-PBE-vdW density functional or the MB-pol force field. Computing the XES spectrum using all molecules in a snapshot results in only one peak in the lone-pair (1b 1) region, while the experiment shows two peaks separated by 0.8-0.9 eV. Different H-bond configurations were classified based on the local structure index (LSI) and a geometrical H-bond cone criterion. We find that tetrahedrally coordinated molecules characterized by high LSI values and two strong donated and two strong accepted H-bonds contribute to the low energy 1b 1 emission peak and to the post-edge region in absorption. Molecules with the asymmetric H-bond environment with one strong accepted H-bond and one strong donated H-bond and low LSI values give rise to the high energy 1b 1 peak in the emission spectrum and mainly contribute to the pre-edge and main-edge in the absorption spectrum. The 1b 1 peak splitting can be increased to 0.62 eV by imposing constraints on the H-bond length, i.e., for very tetrahedral structures short H-bonds (lessmore » than 2.68 Å) and for very asymmetric structures elongated H-bonds (longer than 2.8 Å). Such structures are present, but underrepresented, in the simulations which give more of an average of the two extremes.« less
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  1. Stockholm Univ. (Sweden). Dept. of Physics and AlbaNova Univ. Center
  2. Univ. of Nottingham (United Kingdom). School of Chemistry
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford PULSE Inst.; Heidelberg Univ. (Germany). Interdisciplinary Center for Scientific Computing
Publication Date:
Grant/Contract Number:
AC02-76SF00515; 2015-009559; RF-2014-231
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 148; Journal Issue: 14; Journal ID: ISSN 0021-9606
American Institute of Physics (AIP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE; Swedish Research Council (SRC); Swedish National Infrastructure for Computing (SNIC); Leverhulme Trust
Country of Publication:
United States
74 ATOMIC AND MOLECULAR PHYSICS; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Hydrogen bonding; Absorption spectroscopy; Density functional theory; X-rays; Molecular dynamics; Classical statistical mechanics; Absorption spectra; Emission spectra
OSTI Identifier: