Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water
2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 44, 19997-20007 p.Article in journal (Refereed) Published
We have developed wide-angle X-ray diffraction measurements with high energy-resolution and accuracy to study water structure at three different temperatures (7, 25 and 66 degrees C) under normal pressure. Using a spherically curved Ge crystal an energy resolution better than 15 eV has been achieved which eliminates influence from Compton scattering. The high quality of the data allows for a reliable Fourier transform of the experimental data resolving shell structure out to similar to 12 angstrom, i.e. 5 hydration shells. Large-scale molecular dynamics (MD) simulations using the TIP4P/2005 force-field reproduce excellently the experimental shell-structure in the range 4-12 angstrom although less agreement is seen for the first peak in the intermolecular pair-correlation function (PCF). The Shiratani-Sasai Local Structure Index [J. Chem. Phys. 104, 7671 (1996)] identifies a tetrahedral minority giving the intermediate-range oscillations in the O-O PCF and a disordered majority providing a more featureless background in this range. The current study supports the proposal that the structure of liquid water, even at high temperatures, can be described in terms of a two-state fluctuation model involving local structures related to the high-density and low-density forms of liquid water postulated in the liquid-liquid phase transition hypothesis.
Place, publisher, year, edition, pages
2011. Vol. 13, no 44, 19997-20007 p.
Physical Chemistry Atom and Molecular Physics and Optics
IdentifiersURN: urn:nbn:se:su:diva-71018DOI: 10.1039/c1cp22804hISI: 000296383100038OAI: oai:DiVA.org:su-71018DiVA: diva2:483653