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ATTENTION !!! Changement de date !!! Microscopic structure of water at high pressure and high temperature

Mardi 19 novembre 2013 10:30 - Duree : 1 heure
Lieu : Room 500 - 501, Central Building, ESRF - 6 Rue Jules Horowitz - Grenoble

Orateur : Christoph J. SAHLE (Department of Physics, University of Helsinki, Helsinki, Finland)

We explore the atomic structural changes of water under high pressure and high temperature conditions in water using x-ray spectroscopy. Uncovering the structural details of water on a molecular level still poses challenges to researchers today [1]. Various methods, such as x-ray and neutron scattering, optical Raman and NMR spectroscopies, and molecular dynamics simulations, have been used in an attempt to gain information on this elusive subject. However, there has been no consensus on the microscopic structure of water. This is unfortunate, since the question of the structural details of water across its extensive phase space is of great importance. In particular, the high temperature and high pressure regime studied here is of major interest for geoscientists as water plays a key role in heat and mass transfer as well as element fractionation processes in the Earth’s lithosphere [2]. Moreover, supercritical water is used as a reaction medium for chemical and material synthesis, waste destruction, plastics recycling, and biomass processing [3]. I will demonstrate how we used x-ray spectroscopy in conjunction with ab initio molecular dynamics (MD) simulations and density functional theory to meet this compelling question. We find that the experimental water spectra can be interpreted with structural models obtained from the ab initio molecular dynamics simulations. Specifically, the resemblance of the experimental and calculated spectra allows for extraction of detailed structural information from the MD simulations. Thus, we could extensively characterize the atomic structure and bonding topology of this elusive but fundamentally important liquid across a wide range of temperatures and pressures.

[1] Ball P., Nature 452 (2008) 291. [2] H. Keppler, Nature 380 (1996) 237. [3] Akiya N., Savage P. E., Chem. Rev. 102 (2002) 2725-2750. [4] Schülke W., Oxford University Press (2007)

Contact : eva.jahn@esrf.fr

Discipline évènement : (Physique)
Entité organisatrice : (ESRF)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire ESRF)
Site de l'évènement : Polygone scientifique

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