| 1. |
- Huang, Ningdong, et al.
(författare)
-
X-ray Raman scattering provides evidence for interfacial acetonitrile-water dipole interactions in aqueous solutions
- 2011
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 135:16, s. 164509-
-
Tidskriftsartikel (refereegranskat)abstract
- Aqueous solutions of acetonitrile (MeCN) have been studied with oxygen K-edge x-ray Raman scattering (XRS) which is found to be sensitive to the interaction between water and MeCN. The changes in the XRS spectra can be attributed to water directly interacting with MeCN and are reproduced by density functional theory calculations on small clusters of water and MeCN. The dominant structural arrangement features dipole interaction instead of H-bonds between the two species as revealed by the XRS spectra combined with spectrum calculations. Small-angle x-ray scattering shows the largest heterogeneity for a MeCN to water ratio of 0.4 in agreement with earlier small-angle neutron scattering data.
|
|
| 2. |
- Huang, Congcong, et al.
(författare)
-
Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water
- 2011
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 13:44, s. 19997-20007
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 3. |
- Waluyo, Iradwikanari, et al.
(författare)
-
The structure of water in the hydration shell of cations from x-ray Raman and small angle x-ray scattering measurements
- 2011
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:6, s. 064513-
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray Raman scattering (XRS) spectroscopy and small angle x-ray scattering (SAXS) are used to study water in aqueous solutions of NaCl, MgCl2, and AlCl3 with the particular aim to provide information about the structure of the hydration shells of the cations. XRS spectra show that Na+ weakens the hydrogen bonds of water molecules in its vicinity, similar to the effect of increased temperature and pressure. Mg2+ and Al3+, on the other hand, cause formation of short and strong hydrogen bonds between the surrounding water molecules. SAXS data show that Mg2+ and Al3+ form tightly bound hydration shells that give a large density contrast in the scattering data. From the form factor extracted from the SAXS data, we found that Mg2+ and Al3+ have, respectively, an equivalent of one and one and a half stable hydration shells that appear as a density contrast. In addition, we estimated that the density of water in the hydration shells of Mg2+ and Al3+ is, respectively, ~61% and ~71% higher than in bulk water.
|
|
