Researchers develop procedure to interpret x-ray emission spectra of
liquid water

Date:
March 1, 2022
Source:
Hiroshima University
Summary:
Water is an abundant and essential compound, found everywhere
on Earth.

Yet despite its familiarity and simple structure, water displays
many unusual physical properties. For more than a century,
scientists have turned their attention to the study of water,
attempting to better interpret its structure.



FULL STORY ========================================================================== Water is an abundant and essential compound, found everywhere on
Earth. Yet despite its familiarity and simple structure, water displays
many unusual physical properties. For more than a century, scientists
have turned their attention to the study of water, attempting to better interpret its structure.

An international team of researchers, led by a scholar from Hiroshima University, has developed a procedure allowing them to reproduce the
double peak feature of x-ray emission spectroscopy (XES) spectra in
liquid water.


==========================================================================
The study helping to advance the understanding of the structure of water,
led by Osamu Takahashi, an associate professor at Hiroshima University's Graduate School of Advanced Science and Engineering, is published on
February 25 in Physical Review Letters.

Through the years, as scientists have worked to better understand the
structure of liquid water, some have studied water using a two-structure
model. Other scientists, in a wide range of fields, have used a
uniform, continuous liquid model. XES has proven to be a useful tool
for researchers studying substances whose features are not homogeneous.

For over a decade, scientists have debated how to interpret XES spectra
of liquid water. To solve this problem the research team performed
molecular dynamics calculations to create the model structures of liquid
water. Their next step was to estimate XES spectra for the liquid water,
using first principles of quantum mechanical calculations.

The team was able to theoretically reproduce the double 1b1 feature,
present in liquid water's x-ray emission spectroscopy. They explored
different effects, such as geometry and dynamics, to determine the shape
of the XES spectra.

Adopting classical molecular dynamics simulations, the team was able
to construct the water's structure in the liquid phase. In these
simulations, the researchers worked at various temperature points with
the bond length and water molecule angles fixed. In the spectra they calculated, the researchers were able to reproduce the features, such
as the double peaks of the 1b1 state, that had been previously observed
by other scientists in experimental XES spectra.

To better understand the features they were seeing, the research team classified the XES spectra they calculated based on the different types
of hydrogen bonds. They observed the double peak feature in the XES
spectra in all the different types of hydrogen bonds they studied.

After examining the spectra related to the hydrogen bonds, the team
studied the effect of thermally excited vibrational modes on the XES
spectra. They obtained nine independent vibrational modes and studied
their effects on the spectra.

The researchers were able to successfully reproduce the XES spectra
of liquid water by examining the effect of full vibrational modes,
O-H stretching, bending, and rotational modes. They explained both
the temperature and isotope dependence by examining the hydrogen-bond configuration around the excited water molecule and core-hole induced
dynamics. "Our procedure is general and can be applicable for various
systems related to the phenomena including liquid water," Takahashi said.

The team is hopeful that their research may help to resolve some of
the long- standing debates surrounding the interpretation of liquid
water's structure.

Looking to the future, the researchers see various potential applications
for their procedure. "Development of new materials such as electrodes
used in batteries, biomaterials such as artificial blood vessels, and functional polymers such as water treatment membranes may be fascinating projects, which are related to the structure of liquid water," Takahashi
said.

The research team led by Osamu Takahashi, included Ryosuke Yamamura
from the Department of Chemistry, Hiroshima University, Japan; Takashi Tokushima from MAX IV Laboratory, Lund University, Sweden; and Yoshihisa
Harada from the Institute for Solid State Physics and Synchrotron
Radiation Research Organization, University of Tokyo, Japan. The Japanese Society for the Promotion of Science funded this research.

========================================================================== Story Source: Materials provided by Hiroshima_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Osamu Takahashi, Ryosuke Yamamura, Takashi Tokushima, Yoshihisa
Harada.

Interpretation of the X-Ray Emission Spectra of Liquid Water through
Temperature and Isotope Dependence. Physical Review Letters, 2022;
128 (8) DOI: 10.1103/PhysRevLett.128.086002 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220301093705.htm

--- up 1 day, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)