High resolution X-ray emission spectroscopy of liquid water: The observation of two structural motifs

Tokushima, Takashi; Harada, Yoshihisa; Takahashi, Osamu; Senba, Yasunori; Ohashi, Haruhiko; Pettersson, Lars G. M.; Nilsson, Anders; Shin, Shik

doi:10.1016/j.cplett.2008.04.077

Cited by 354 publications

(480 citation statements)

References 104 publications

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“…It has been suggested that a large fraction of molecules form only two strong HBs: one acceptor and one donor bond 2,152-156 . However, the"rings and chains" structure of liquid water 2 , as well as the inhomogeneous two-state model 152,157 implied by such an interpretation, have been challenged on many fronts 143,147,[158][159][160][161][162][163][164][165][166][167] and are a matter of an ongoing debate 80,143,147,[155][156][157][158][159][160][161][162][163][164][166][167][168][169][170][171][172] .…”

Section: Liquid Water a Structural And Dynamical Properties Of Lmentioning

confidence: 99%

Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies

Khaliullin

Kühne

2013

Phys. Chem. Chem. Phys.

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The application of newly developed first-principle modeling techniques to liquid water deepens our understanding of the microscopic origins of its unusual macroscopic properties and behaviour. Here, we review two novel ab initio computational methods: second-generation Car-Parrinello molecular dynamics and decomposition analysis based on absolutely localized molecular orbitals. We show that these two methods in combination not only enable ab initio molecular dynamics simulations on previously inaccessible time and length scales, but also provide unprecedented insights into the nature of hydrogen bonding between water molecules. We discuss recent applications of these methods to water clusters and bulk water. CONTENTS

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Section: Liquid Water a Structural And Dynamical Properties Of Lmentioning

confidence: 99%

Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies

Khaliullin

Kühne

2013

Phys. Chem. Chem. Phys.

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“…The resolution of the grating spectrometer was 0.4 at 530 eV (oxygen K-edge). The elastic peaks were used for energy calibration and the absolute energy scale in this experiment has been adjusted to Tokushima et al 38 ■ RESULTS AND DISCUSSION Figure 2 shows the X-ray emission spectra for nonresonant as well as resonant excitation at the oxygen K-edge for pure liquid water and aqueous NaCl solution with 2 M concentration.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…38,40,50 Furthermore, molecular dynamic (MD) calculations can qualitatively reproduce the fine structure without including a two component model of liquid water, rather based on ultrafast dynamics during the core-hole lifetime. 48,49 Conclusively, this would predict that the splitting in A is due to different molecular orbitals.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Probing the Hofmeister Effect with Ultrafast Core–Hole Spectroscopy

et al. 2014

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In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt−water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effectif existentmay be caused by more complex interactions. ■ INTRODUCTIONAt the end of the 19th century, Franz Hofmeister discovered that common anions and cations could be classified according to their ability to salt in/salt out proteins, in detail to enhance aggregation and precipitation of proteins dissolved in aqueous solution; see Scheme 1. 1 By now, the so-called Hofmeister effect has been observed in a number of systems ranging from atmospheric aerosols up to whole biological entities such as cells, proteins, etc. 2,3 The salting in/out effect even plays an essential role in the metabolism of eukaryotic cells and in the case of mammalians it can lead to critical aggregation effects which were discussed as various prestages of diseases. 4,5 However, the question concerning the effect's origin remains unanswered. Two common models to explain it are (i) water interacting with the hydrated ions and causing precipitation or (ii) a consequence of the direct binding of the salt ions to the biomolecule by electrostatic interactions. 6 The first model leads to the concept of structure makers/ structure breakers (SMB), depending on the anions and cations used. According to this concept, cations and anions stabilize or destabilize the long-range water structure in aqueous solutions, 7 which is conventionally interpreted as strengthening and weakening of the hydrogen bond structure. 8 Theories based on molecular dynamic calculations have been introduced to explain the nature of the effect, some supporting the concept of structure breaking and making, 9−11 some contradicting. 12−15 However, there is a lack of understanding on the molecular level, since SMB is based on experimental observations of macroscopic properties. 16,17 Several experiments have been performed recently regarding the validation of SMB on the molecular level, which reveal objecting results. 8,18−30 Yet, the influence of salt ions on the electronic redistribution of water is unclear. In order to probe the electronic influence of salt ions on the water structure and therefore, if the SMB concept can be pictured on the molecular orbitals of the aqueous systems, corehole X-ray emission spectroscopic (XES) measurements have been performed on the oxygen K-edge of pure water and aqueous salt solutions.

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“…In liquid water, depending on the temperature, this may give rise to different hydrogen bonding motifs, which at ambient conditions seem to coexist as structural and dynamic heterogeneities. [3][4][5] Going down to the supercooled regime, these heterogeneities appear to be more pronounced, [6][7][8] and it is hypothesized that they can be understood as the residual of two distinct liquid phases. 9,10 One way to acquire information about this hydrogen bonding network is to monitor the changes of the OH (or OD) stretch frequency.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Infrared Spectroscopy of Supercooled Water

Perakis

Hamm

2010

J. Phys. Chem. B

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We present two-dimensional infrared (2D IR) spectra of the OD stretch vibration of isotope diluted water (HOD/H2O) from ambient conditions (293 K) down to the metastable supercooled regime (260 K). We observe that spectral diffusion slows down from 700 fs to 2.6 ps as we lower the temperature. A comparison between measurements performed at the magic angle with those at parallel polarization shows that the 2D IR line shape is affected by the frequency-dependent anisotropy decay in the case of parallel polarization, altering the extracted correlation decay. A fit within the framework of an Arrhenius law reveals an activation energy of Ea = 6.2 ± 0.2 kcal/mol and a pre-exponential factor of 1/A = 0.02 ± 0.01 fs. Alternatively, a power law fit results in an exponent γ = 2.2 and a singularity temperature Ts = 221 K. We tentatively conclude that the power law provides the better physical picture to describe the dynamics of liquid water around the freezing point. 2D IR spectroscopy of supercooled water AbstractWe present 2D IR spectra of the OD stretch vibration of isotope diluted water (HOD/H 2 O) from ambient conditions (293 K) down to the metastable supercooled regime (260 K). We observe that spectral diffusion slows down from 700 fs to 2.6 ps as we lower the temperature.Comparison between measurements performed at magic angle with those at parallel polarization shows that the 2D IR lineshape is affected by the frequency dependent anisotropy decay in the case of parallel polarization, altering the extracted correlation decay. A fit within the framework of an Arrhenius law reveals an activation energy of E a = 6.2 ± 0.2 kcal/mol and a pre-exponential factor of 1/A = 0.02 ± 0.01 fs. Alternatively, a power law fit results in an exponent γ = 2.2 and a singularity temperature T s = 221 K. We tentatively conclude that the power law provides the better physical picture to describe the dynamics of liquid water around the freezing point.

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High resolution X-ray emission spectroscopy of liquid water: The observation of two structural motifs

Cited by 354 publications

References 104 publications

Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies

Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies

Probing the Hofmeister Effect with Ultrafast Core–Hole Spectroscopy

Two-Dimensional Infrared Spectroscopy of Supercooled Water

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