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  • 1.
    Amann-Winkel, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bellissent-Funel, Marie-Claire
    Bove, Livia E.
    Loerting, Thomas
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Paciaroni, Alessandro
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Skinner, Lawrie
    X-ray and Neutron Scattering of Water2016In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 116, no 13, p. 7570-7589Article, review/survey (Refereed)
    Abstract [en]

    This review article focuses on the most recent advances in X-ray and neutron scattering studies of water structure, from ambient temperature to the deeply supercooled and amorphous states, and of water diffusive and collective dynamics, in disparate thermodynamic conditions and environments. In particular, the ability to measure X-ray and neutron diffraction of water with unprecedented high accuracy in an extended range of momentum transfers has allowed the derivation of detailed O-O pair correlation functions. A panorama of the diffusive dynamics of water in a wide range of temperatures (from 400 K down to supercooled water) and pressures (from ambient up to multiple gigapascals) is presented. The recent results obtained by quasi-elastic neutron scattering under high pressure are compared with the existing data from nuclear magnetic resonance, dielectric and infrared measurements, and modeling. A detailed description of the vibrational dynamics of water as measured by inelastic neutron scattering is presented. The dependence of the water vibrational density of states on temperature and pressure, and in the presence of biological molecules, is discussed. Results about the collective dynamics of water and its dispersion curves as measured by coherent inelastic neutron scattering and inelastic X-ray scattering in different thermodynamic conditions are reported.

  • 2.
    Camisasca, Gaia
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Zhovtobriukh, Iurii
    Stockholm University, Faculty of Science, Department of Physics.
    Pitsevich, George
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    A proposal for the structure of high- and low-density fluctuations in liquid water2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 3, article id 034508Article in journal (Refereed)
    Abstract [en]

    Based on recent experimental data that can be interpreted as indicating the presence of specific structures in liquid water, we build and optimize two structural models which we compare with the available experimental data. To represent the proposed high-density liquid structures, we use a model consisting of chains of water molecules, and for low-density liquid, we investigate fused dodecahedra as templates for tetrahedral fluctuations. The computed infrared spectra of the models are in very good agreement with the extracted experimental spectra for the two components, while the extracted structures from molecular dynamics (MD) simulations give spectra that are intermediate between the experimentally derived spectra. Computed x-ray absorption and emission spectra as well as the O-O radial distribution functions of the proposed structures are not contradicted by experiment. The stability of the proposed dodecahedral template structures is investigated in MD simulations by seeding the starting structure, and remnants found to persist on an similar to 30 ps time scale. We discuss the possible significance of such seeds in simulations and whether they can be viable candidates as templates for structural fluctuations below the compressibility minimum of liquid water.

  • 3.
    Dalirian, Maryam
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ylisirniö, Arttu
    Buchholz, Angela
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Virtanen, Annele
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Cloud droplet activation of black carbon particles coated with organic compounds of varying solubility2018In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 18, no 16, p. 12477-12489Article in journal (Refereed)
    Abstract [en]

    Atmospheric black carbon (BC) particles are a concern due to their impact on air quality and climate. Their net climate effect 15 is, however, still uncertain. This uncertainty is partly related to the contribution of coated BC-particles to the global CCN budgets. In this study, laboratory measurements were performed to investigate cloud condensation nuclei (CCN) activity of BC (Regal black) particles, in pure state or coated through evaporating and subsequent condensation of glutaric acid, levoglucosan (both water-soluble organics) or oleic acid (an organic compound with low solubility). A combination of Soot Particle Aerosol Mass Spectrometer (SP-AMS) measurements and size distribution measurements with Scanning Mobility 20 Particle Sizer (SMPS) showed that the studied BC particles were nearly spherical agglomerates with a fractal dimension of 2.79 and that they were coated evenly by the organic species. The CCN activity of BC particles increased after coating with all the studied compounds and was governed by the fraction of organic material. The CCN activation of the BC particles coated by glutaric acid and levoglucosan were in good agreement with the theoretical calculations using shell-and-core model, which is based on a combination of the CCN activities of the pure compounds. The oleic acid coating enhanced the CCN 25 activity of the BC particles, even though the pure oleic acid particles were CCN inactive. The surprising effect of oleic acid might be related to the arrangement of the oleic acid molecules on the surface of the BC cores or other surface phenomena facilitating water condensation onto the coated particles. Our results show potential in accurately predicting the CCN activity of atmospheric BC coated with organic species by present theories, given that the identities and amount of the coating species are known. Furthermore, our results suggest that even relatively thin soluble coatings (around 2 nm for the compounds studied here) are enough to make the insoluble BC particles CCN active at typical atmospheric supersaturations and thus be efficiently taken up by cloud droplets. This highlights the need of an accurate description of the composition of atmospheric particles containing BC to unravel their net impact on climate.

  • 4.
    Huang, Ningdong
    et al.
    Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA.
    Nordlund, Dennis
    Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA.
    Huang, Congcong
    Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA.
    Tyliszczak, Tolek
    LBL, Adv Light Source, Berkeley, CA 94720 USA .
    Weiss, Thomas M.
    Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA .
    Acremann, Yves
    Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA .
    Pettersson, Lars G.M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Microscopic Probing of the Size Dependence in Hydrophobic Solvation2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 136, no 7, p. 074507-Article in journal (Refereed)
    Abstract [en]

    A dependence on solute size of the hydrophobic effect has been proposed based on theory and simulations, such that small apolar solutes leave the hydrogen (H-) bonding network in water intact or even strengthened, whereas hydration of larger, nanometer-sized apolar solutes breaks hydrogen bonds and creates a liquid-vapor-like interface around the solutes. Here we report the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in aqueous solutions of amphiphilic tetraalkyl-ammonium (CnH2n+1)4N + (TAA) cations with increased side chain length by probing the H-bonding network in water through O K-edge x-ray absorption spectroscopy and the solute-solute interaction using small angle x-ray scattering. These results open for unique experimental opportunities to investigate hydrophobic effects for a range of important processes in chemistry and biology.

    We report small angle x-ray scattering data demonstrating the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in hydrophobic solvation. By increasing the side chain length of amphiphilic tetraalkyl-ammonium (CnH2n+1)4N+ (R4N+) cations in aqueous solution we observe diffraction peaks indicating association between cations at a solute size between 4.4 and 5 Å, which show temperature dependence dominated by hydrophobic attraction. Using O K-edge x-ray absorption we show that small solutes affect hydrogen bonding in water similar to a temperature decrease, while large solutes affect water similar to a temperature increase. Molecular dynamics simulations support, and provide further insight into, the origin of the experimental observations.

  • 5. Kaya, Sarp
    et al.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Yamamoto, Susumu
    Newberg, John T.
    Bluhm, Hendrik
    Ogasawara, Hirohito
    Kendelewicz, Tom
    Brown, Gordon E., Jr.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Highly Compressed Two-Dimensional Form of Water at Ambient Conditions2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, article id 1074Article in journal (Refereed)
    Abstract [en]

    The structure of thin-film water on a BaF2(111) surface under ambient conditions was studied using x-ray absorption spectroscopy from ambient to supercooled temperatures at relative humidity up to 95%. No hexagonal ice-like structure was observed in spite of the expected templating effect of the lattice-matched (111) surface. The oxygen K-edge x-ray absorption spectrum of liquid thin-film water on BaF2 exhibits, at all temperatures, a strong resemblance to that of high-density phases for which the observed spectroscopic features correlate linearly with the density. Surprisingly, the highly compressed, high-density thin-film liquid water is found to be stable from ambient (300 K) to supercooled (259 K) temperatures, although a lower-density liquid would be expected at supercooled conditions. Molecular dynamics simulations indicate that the first layer water on BaF2(111) is indeed in a unique local structure that resembles high-density water, with a strongly collapsed second coordination shell.

  • 6. Kumar, P.
    et al.
    Wikfeldt, Kjartan Thor
    Stockholm University, Faculty of Science, Department of Physics.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Stanley, H. E.
    Possible origin of low-frequency excitations in supercooled bulk and protein-hydration waterManuscript (preprint) (Other academic)
  • 7. Kumar, Pradeep
    et al.
    Wikfeldt, Thor Kjartan
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Iceland, Iceland.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Stanley, H. Eugene
    The Boson peak in supercooled water2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, article id 1980Article in journal (Refereed)
    Abstract [en]

    We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores, and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line T-W. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.

  • 8. Laksmono, Hartawan
    et al.
    McQueen, Trevor A.
    Sellberg, Jonas A.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Loh, N. Duane
    Huang, Congcong
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Sierra, Raymond G.
    Hampton, Christina Y.
    Nordlund, Dennis
    Beye, Martin
    Martin, Andrew V.
    Barty, Anton
    Seibert, M. Marvin
    Messerschmidt, Marc
    Williams, Garth J.
    Boutet, Sebastien
    Arnann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics. University of Innsbruck, Austria.
    Loerting, Thomas
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Bogan, Michael J.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA; .
    Anomalous Behavior of the Homogeneous Ice Nucleation Rate in No-Man's Land2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 14, p. 2826-2832Article in journal (Refereed)
    Abstract [en]

    We present an analysis of ice nucleation kinetics from near-ambient pressure water as temperature decreases below the homogeneous limit T-H by cooling micrometer-sized droplets (microdroplets) evaporatively at 10(3)-10(4) K/s and probing the structure ultrafast using femtosecond pulses from the Linac Coherent Light Source (LCLS) free-electron X-ray laser. Below 232 K, we observed a slower nucleation rate increase with decreasing temperature than anticipated from previous measurements, which we suggest is due to the rapid decrease in water's diffusivity. This is consistent with earlier findings that microdroplets do not crystallize at <227 K, but vitrify at cooling rates of 10(6)-10(7) K/s. We also hypothesize that the slower increase in the nucleation rate is connected with the proposed fragile-to-strong transition anomaly in water.

  • 9.
    Mariedahl, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Perakis, Fivos
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Kim, Kyung Hwan
    Stockholm University, Faculty of Science, Department of Physics.
    Camisasca, Gaia
    Stockholm University, Faculty of Science, Department of Physics.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Benmore, Chris
    Pettersson, Lars Gunnar Moody
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Arnann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    X-ray Scattering and O-O Pair-Distribution Functions of Amorphous Ices2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 30, p. 7616-7624Article in journal (Refereed)
    Abstract [en]

    The structure factor and oxygen-oxygen pair distribution functions of amorphous ices at liquid nitrogen temperature (T = 77 K) have been derived from wide-angle X-ray scattering (WAXS) up to interatomic distances of r = 23 angstrom, where local structure differences between the amorphous ices can be seen for the entire range. The distances to the first coordination shell for low-, high-, and very-high-density amorphous ice (LDA, HDA, VHDA) were determined to be 2.75, 2.78, and 2.80 angstrom, respectively, with high accuracy due to measurements up to a large momentum transfer of 23 angstrom(-1). Similarities in pair-distribution functions between LDA and supercooled water at 254.1 K, HDA and liquid water at 365.9 K, and VHDA and high-pressure liquid water were found up to around 8 angstrom, but beyond that at longer distances, the similarities were lost. In addition, the structure of the high-density amorphous ices was compared to high-pressure crystalline ices IV, IX, and XII, and conclusions were drawn about the local ordering.

  • 10.
    Nilsson, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    X-ray and simulation studies of water2016In: La Rivista del nuovo cimento della Società italiana di fisica, ISSN 0393-697X, E-ISSN 1826-9850, Vol. 39, no 5, p. 225-278Article in journal (Refereed)
    Abstract [en]

    Here we present a picture that combines discussions regarding the thermodynamic anomalies in ambient and supercooled water with recent interpretations of X-ray spectroscopy and scattering data of water. At ambient temperatures most molecules favor a closer packing than tetrahedral, with strongly distorted hydrogen bonds, which allows the quantized librational modes to be excited and contribute to the entropy, but with enthalpically favored tetrahedrally bonded water patches appearing as fluctuations, i.e. a competition between entropy and enthalpy. Upon cooling water the amount of molecules participating in tetrahedral structures and the size of the tetrahedral patches increase. The two local structures are connected to the liquid-liquid critical point hypothesis in supercooled water corresponding to high-density liquid (HDL) and low-density liquid (LDL). We demonstrate that the HDL local structure deviates from a tetrahedral coordination not only through a collapse of the 2nd shell but also through severe distortions around the 1st coordination shell.

  • 11.
    Pathak, Harshad
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Palmer, J. C.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Wikfeldt, Kjartan Thor
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, J. A.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    The structural validity of various thermodynamical models of supercooled water2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 13, article id 134507Article in journal (Refereed)
    Abstract [en]

    The thermodynamic response functions of water exhibit an anomalous increase upon cooling that becomes strongly amplified in the deeply supercooled regime due to structural fluctuations between disordered and tetrahedral local structures. Here, we compare structural data from recent x-ray laser scattering measurements of water at 1 bar and temperatures down to 227 K with structural properties computed for several different water models using molecular dynamics simulations. Based on this comparison, we critically evaluate four different thermodynamic scenarios that have been invoked to explain the unusual behavior of water. The critical point-free model predicts small variations in the tetrahedrality with decreasing temperature, followed by a stepwise change at the liquid-liquid transition around 228 K at ambient pressure. This scenario is not consistent with the experimental data that instead show a smooth and accelerated variation in structure from 320 to 227 K. Both the singularity-free model and ice coarsening hypothesis give trends that indirectly indicate an increase in tetrahedral structure with temperature that is too weak to be consistent with experiment. A model that includes an apparent divergent point (ADP) at high positive pressure, however, predicts structural development consistent with our experimental measurements. The terminology ADP, instead of the commonly used liquid-liquid critical point, is more general in that it focuses on the growing fluctuations, whether or not they result in true criticality. Extrapolating this model beyond the experimental data, we estimate that an ADP in real water may lie around 1500 +/- 250 bars and 190 +/- 6 K.

  • 12.
    Perakis, Fivos
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Amann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics.
    Lehmkühler, Felix
    Sprung, Michael
    Mariedahl, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Pathak, Harshad
    Stockholm University, Faculty of Science, Department of Physics.
    Späh, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Cavalca, Filippo
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Ricci, Alessandro
    Jain, Avni
    Massani, Bernhard
    Aubree, Flora
    Benmore, Chris J.
    Loerting, Thomas
    Grübel, Gerhard
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Diffusive dynamics during the high-to-low density transition in amorphous ice2017In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 114, no 31, p. 8193-8198Article in journal (Refereed)
    Abstract [en]

    Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high(HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid-liquid transition in the ultraviscous regime.

  • 13. Ros, Katrin
    et al.
    Johansen, Anders
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Tampere University of Technology, Finland.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Effect of nucleation on icy pebble growth in protoplanetary discs2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 629, article id A65Article in journal (Refereed)
    Abstract [en]

    Solid particles in protoplanetary discs can grow by direct vapour deposition outside of ice lines. The presence of microscopic silicate particles may nevertheless hinder growth into large pebbles, since the available vapour is deposited predominantly on the small grains that dominate the total surface area. Experiments on heterogeneous ice nucleation, performed to understand ice clouds in the Martian atmosphere, show that the formation of a new ice layer on a silicate surface requires a substantially higher water vapour pressure than the deposition of water vapour on an existing ice surface. In this paper, we investigate how the difference in partial vapour pressure needed for deposition of vapour on water ice versus heterogeneous ice nucleation on silicate grains influences particle growth close to the water ice line. We developed and tested a dynamical 1D deposition and sublimation model, where we include radial drift, sedimentation, and diffusion in a turbulent protoplanetary disc. We find that vapour is deposited predominantly on already ice-covered particles, since the vapour pressure exterior of the ice line is too low for heterogeneous nucleation on bare silicate grains. Icy particles can thus grow to centimetre-sized pebbles in a narrow region around the ice line, whereas silicate particles stay dust-sized and diffuse out over the disc. The inhibition of heterogeneous ice nucleation results in a preferential region for growth into planetesimals close to the ice line where we find large icy pebbles. The suppression of heterogeneous ice nucleation on silicate grains may also be the mechanism behind some of the observed dark rings around ice lines in protoplanetary discs, as the presence of large ice pebbles outside ice lines leads to a decrease in the opacity there.

  • 14.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Molecular structure and dynamics of liquid water: Simulations complementing experiments2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Water is abundant on earth and in the atmosphere and the most crucial liquid for life as we know it. It has been subject to rather intense research since more than a century and still holds secrets about its molecular structure and dynamics, particularly in the supercooled state, i. e. the metastable liquid below its melting point. 

    This thesis is concerned with different aspects of water and is written from a theoretical perspective. Simulation techniques are used to study structures and processes on the molecular level and to interpret experimental results. The evaporation kinetics of tiny water droplets is investigated in simulations with focus on the cooling process associated with evaporation. The temperature evolution of nanometer-sized droplets evaporating in vacuum is well described by the Knudsen theory of evaporation. The principle of evaporative cooling is used in experiments to rapidly cool water droplets to extremely low temperatures where water transforms into a highly structured low-density liquid in a continuous and accelerated fashion.

    For water at ambient conditions, a structural standard is established in form of a high precision radial distribution function as a result of x-ray diffraction experiments and simulations. Recent data even reveal intermediate range molecular correlations to distances of up to 17 Å in the bulk liquid.

    The barium fluoride (111) crystal surface has been suggested to be a template for ice formation because its surface lattice parameter almost coincides with that of the basal plane of hexagonal ice. Instead, water at the interface shows structural signatures of a high-density liquid at ambient and even at supercooled conditions.

    Inelastic neutron scattering experiments have shown a feature in the vibrational spectra of supercooled confined and protein hydration water which is connected to the so-called Boson peak of amorphous materials. We find a similar feature in simulations of bulk supercooled water and its emergence is associated with the transformation into a low-density liquid upon cooling.

  • 15.
    Schlesinger, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Evaporative cooling of microscopic water droplets in vacuo: Molecular dynamics simulations and kinetic gas theory2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 12Article in journal (Refereed)
    Abstract [en]

    In the present study, we investigate the process of evaporative cooling of nanometer-sized droplets in vacuum using molecular dynamics simulations with the TIP4P/2005 water model. The results are compared to the temperature evolution calculated from the Knudsen theory of evaporation which is derived from kinetic gas theory. The calculated and simulation results are found to be in very good agreement for an evaporation coefficient equal to unity. Our results are of interest to experiments utilizing droplet dispensers as well as to cloud micro-physics.

  • 16.
    Schlesinger, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Sellberg, Jonas A.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Evaporative cooling of microscopic water droplets in vacuo: Molecular dynamics simulations and kinetic gas theoryManuscript (preprint) (Other academic)
  • 17.
    Schlesinger, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Wikfeldt, K. Thor
    Stockholm University, Faculty of Science, Department of Physics.
    Skinner, Lawrie B.
    Benmore, Chris J.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    The temperature dependence of intermediate range oxygen-oxygen correlations in liquid water2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 8, article id 084503Article in journal (Refereed)
    Abstract [en]

    We analyze the recent temperature dependent oxygen-oxygen pair-distribution functions from experimental high-precision x-ray diffraction data of bulk water by Skinner et al. [J. Chem. Phys. 141, 214507 (2014)] with particular focus on the intermediate range where small, but significant, correlations are found out to 17 angstrom. The second peak in the pair-distribution function at 4.5 angstrom is connected to tetrahedral coordination and was shown by Skinner et al. to change behavior with temperature below the temperature of minimum isothermal compressibility. Here we show that this is associated also with a peak growing at 11 angstrom which strongly indicates a collective character of fluctuations leading to the enhanced compressibility at lower temperatures. We note that the peak at similar to 13.2 angstrom exhibits a temperature dependence similar to that of the density with a maximum close to 277 K or 4 degrees C. We analyze simulations of the TIP4P/2005 water model in the same manner and find excellent agreement between simulations and experiment albeit with a temperature shift of similar to 20 K.

  • 18.
    Schlesinger, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Wikfeldt, Kjartan Thor
    Stockholm University, Faculty of Science, Department of Physics.
    Skinner, Lawrie B.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Intermediate range molecular correlations in liquid waterManuscript (preprint) (Other academic)
  • 19. Schreck, Simon
    et al.
    Beye, Martin
    Sellberg, Jonas A.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    McQueen, Trevor
    Laksmono, Hartawan
    Kennedy, Brian
    Eckert, Sebastian
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Nordlund, Dennis
    Ogasawara, Hirohito
    Sierra, Raymond G.
    Segtnan, Vegard H.
    Kubicek, Katharina
    Schlotter, William F.
    Dakovski, Georgi L.
    Moeller, Stefan P.
    Bergmann, Uwe
    Techert, Simone
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Wernet, Philippe
    Bogan, Michael J.
    Harada, Yoshihisa
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Foehlisch, Alexander
    Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences2014In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 113, no 15, p. 153002-Article in journal (Refereed)
    Abstract [en]

    We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.

  • 20.
    Sellberg, Jonas A.
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Huang, C.
    McQueen, T. A.
    Loh, N. D.
    Laksmono, H.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Sierra, R. G.
    Nordlund, D.
    Hampton, C. Y.
    Starodub, D.
    DePonte, D. P.
    Beye, M.
    Chen, C.
    Martin, A. V.
    Barty, A.
    Wikfeldt, Kjartan Thor
    Stockholm University, Faculty of Science, Department of Physics.
    Weiss, T. M.
    Caronna, C.
    Feldkamp, J.
    Skinner, L. B.
    Seibert, M. M.
    Messerschmidt, M.
    Williams, G. J.
    Boutet, S.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Bogan, M. J.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Ultrafast X-ray probing of water structure below the homogeneous ice nucleation temperature2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 510, no 7505, p. 381-+Article in journal (Refereed)
    Abstract [en]

    Water has a number of anomalous physical properties, and some of these become drastically enhanced on supercooling below the freezing point. Particular interest has focused on thermodynamic response functions that can be described using a normal component and an anomalous component that seems to diverge at about 228 kelvin (refs 1-3). This has prompted debate about conflicting theories(4-12) that aim to explain many of the anomalous thermodynamic properties of water. One popular theory attributes the divergence to a phase transition between two forms of liquid water occurring in the 'no man's land' that lies below the homogeneous ice nucleation temperature (T-H) at approximately 232 kelvin(13) and above about 160 kelvin(14), and where rapid ice crystallization has prevented any measurements of the bulk liquid phase. In fact, the reliable determination of the structure of liquid water typically requires temperatures above about 250 kelvin(2,15). Water crystallization has been inhibited by using nanoconfinement(16), nanodroplets(17) and association with biomolecules(16) to give liquid samples at temperatures below T-H, but such measurements rely on nanoscopic volumes of water where the interaction with the confining surfaces makes the relevance to bulk water unclear(18). Here we demonstrate that femtosecond X-ray laser pulses can be used to probe the structure of liquid water in micrometre-sized droplets that have been evaporatively cooled(19-21) below TH. We find experimental evidence for the existence of metastable bulk liquid water down to temperatures of 227(-1)(+2) kelvin in the previously largely unexplored no man's land. We observe a continuous and accelerating increase in structural ordering on supercooling to approximately 229 kelvin, where the number of droplets containing ice crystals increases rapidly. But a few droplets remain liquid for about a millisecond even at this temperature. The hope now is that these observations and our detailed structural data will help identify those theories that best describe and explain the behaviour of water.

  • 21.
    Sellberg, Jonas A.
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    McQueen, Trevor A.
    Laksmono, Hartawan
    Schreck, Simon
    Beye, Martin
    DePonte, Daniel P.
    Kennedy, Brian
    Nordlund, Dennis
    Sierra, Raymond G.
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Tokushima, Takashi
    Zhovtobriukh, Iurii
    Stockholm University, Faculty of Science, Department of Physics.
    Eckert, Sebastian
    Segtnan, Vegard H.
    Ogasawara, Hirohito
    Kubicek, Katharina
    Techert, Simone
    Bergmann, Uwe
    Dakovski, Georgi L.
    Schlotter, William F.
    Harada, Yoshihisa
    Bogan, Michael J.
    Wernet, Philippe
    Foehlisch, Alexander
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    X-ray emission spectroscopy of bulk liquid water in no-man's land2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, no 4, article id 044505Article in journal (Refereed)
    Abstract [en]

    The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (T-H) of similar to 232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below T-H using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b(1)' and 1b(1) peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important.

  • 22. Skinner, Lawrie B.
    et al.
    Huang, Congcong
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Benmore, Chris J.
    Benchmark oxygen-oxygen pair-distribution function of ambient water from x-ray diffraction measurements with a wide Q-range2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 7, article id 074506Article in journal (Refereed)
    Abstract [en]

    Four recent x-ray diffraction measurements of ambient liquid water are reviewed here. Each of these measurements represents a significant development of the x-ray diffraction technique applied to the study of liquid water. Sources of uncertainty from statistical noise, Q-range, Compton scattering, and self-scattering are discussed. The oxygen-hydrogen contribution to the measured x-ray scattering pattern was subtracted using literature data to yield an experimental determination, with error bars, of the oxygen-oxygen pair-distribution function, g(OO)(r), which essentially describes the distribution of molecular centers. The extended Q-range and low statistical noise of these measurements has significantly reduced truncation effects and related errors in the g(OO)(r) functions obtained. From these measurements and error analysis, the position and height of the nearest neighbor maximum in g(OO)(r) were found to be 2.80(1) angstrom and 2.57(5) respectively. Numerical data for the coherent differential x-ray scattering cross-section I-X(Q), the oxygen-oxygen structure factor S-OO(Q), and the derived g(OO)(r) are provided as benchmarks for calibrating force-fields for water.

  • 23. Waluyo, Iradwikanari
    et al.
    Nordlund, Dennis
    Bergmann, Uwe
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    A different view of structure-making and structure-breaking in alkali halide aqueous solutions through x-ray absorption spectroscopy2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 24, p. 244506-Article in journal (Refereed)
    Abstract [en]

    X-ray absorption spectroscopy measured in transmission mode was used to study the effect of alkali and halide ions on the hydrogen-bonding (H-bonding) network of water. Cl- and Br- are shown to have insignificant effect on the structure of water while I-locally weakens the H-bonding, as indicated by a sharp increase of the main-edge feature in the x-ray absorption spectra. All alkali cations act as structure-breakers in water, weakening the H-bonding network. The spectral changes are similar to spectra of high density ices where the 2nd shell has collapsed due to a break-down of the tetrahedral structures, although here, around the ions, the breakdown of the local tetrahedrality is rather due to non-directional H-bonding to the larger anions. In addition, results from temperature-dependent x-ray Raman scattering measurements of NaCl solution confirm the H-bond breaking effect of Na+ and the effect on the liquid as similar to an increase in temperature.

1 - 23 of 23
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